Live Coverage: Australian Open - Day Eight - as it happened

Hello everyone. The Australian Open just keeps on rolling. There were wins for Maria Sharapova, Rafael Nadal, Andy Murray and a number of the sport's other top stars yesterday, and the race for a spot in the quarter-finals continues today. We'll have all of the latest news, results and game-by-game coverage of the key matches right here.

The first match of the day - Dominika Cibulkova vs. Victoria Azarenka - is just a few moments away, but there's plenty more action to come when that fourth-round clash finishes. At around 1.30am we'll be turning our attention to Serena Williams, who takes on Garbine Muguruza.

You can see the day's full schedule below from both the men's and women's draw. Of course, times could change as the day progresses.

MEN'S SINGLES
Wawrinka vs. Garcia-Lopez (2.30am)
Ferrer vs. Nishikori (3am)
Lopez vs. Raonic (6am)
Djokovic vs. Muller (9.30am)

WOMEN'S SINGLES
Cibulkova vs. Azarenka (12.15am)
S. Williams vs. Muguruza (1.30am)
Keys vs. Brengle (4.15am)
V. Williams vs. Radwanska (8am)

There's actually been quite a bit of rain in Melbourne today, but with three roofs in place across the grounds, there's no chance of us missing out on drama. Azarenka vs. Cibulkova is underway.

I'm sure all of you Brits out there watched Andy Murray produce an impressive display in the latter stages of the fourth set to beat Grigor Dimitrov yesterday, and the sixth seed was unable to hide his own pleasure when reflecting on the performance.

Novak Djokovic will meet the unseeded Gilles Muller in the fourth round later on today, and the world number one has been speaking of his admiration for the 31-year-old.

"He struggled a little bit with injuries the last couple years, but I think the last six months has been playing some of his best tennis," Djokovic told reporters. "[He reached the] semi-finals in Sydney. Now he's in the fourth round winning against some top players. Winning against Isner in straight sets is never easy. He has done that. So he deserves respect. I need to be obviously very alert and hopefully I can return well, which is going to be one of the keys of the match."

SET! What a start from Dominika Cibulkova. The 11th seed was simply too good for Victoria Azarenka in an opening set which she won 6-2, and she is halfway to reaching the last eight.

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SET! That's how you respond. Azarenka was a set down, but she's just served out at the second time of asking to level the scores with success in the second. It goes down to a decider. Cibulkova or Azarenka, who are you backing?

If Andy Murray is to win the Australian Open, he may have to go through Novak Djokovic to get to the title. However, the sixth seed is not the only Brit looking to upset the world number one. Jamie Delgado now works as Gilles Muller's coach, and he believes that their fourth-round clash is will be a big test for Djokovic.

There's more good news for fans of Azarenka. The Belarusian is now up a break in the deciding set, and she's in the driving seat against Cibulkova.

Even during practice, Mr Nadal can't get away from his army of supporters.

A #Rafa's eye view of the world. #ausopen #Nadal #australiaday pic.twitter.com/ju8w1l3jaW — Australian Open (@AustralianOpen) January 26, 2015

Sorry to the Azarenka supporters, it must have been me. Cibulkova has broken back and the fourth-round clash remains finely poised. It's a fantastic way to start day eight of the Australian Open.

One match which should almost certainly deliver drama and some fantastic tennis is tomorrow's quarter-final clash between Maria Sharapova and Eugenie Bouchard. Both women have the potential to dominate rallies, and Bouchard insists that she has no intention of changing her game plan for a meeting with the second seed.

Stanislas Wawrinka is just about to kick things off against Guillermo Garcia-Lopez. Very little seems to have been said about the defending champion, but he's still here, and last year he proved that he can get it done in the big matches.

RESULT! She's done it. Last season's runner-up Dominika Cibulkova is through to the quarter-finals thanks to a 6-2 3-6 6-3 win over two-time champion Victoria Azarenka, whose fine campaign comes to an end. After her 2014 was wrecked by injuries, Azarenka has proved that she is back to somewhere close to her best. However, the day belongs to Cibulkova.

Cibulkova will meet the winner of Serena Williams vs. Garbine Muguruza. A quick reminder that we will have game-by-game coverage. Want some even better news? That match is next up on the Rod Laver Arena.

We'll be very lucky to see a better match than the previous one, but let's hope Williams and Muguruza can go close. As always, Williams head into the match as firm favourite to progress, but Muguruza has shown that she is good enough to test anyone on tour.

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You might remember that Muguruza was responsible for one of the biggest shocks of 2014, and it came against today's opponent. Williams was expected to cruise to victory in the second round of last year's Australian Open, but Muguruza came through with a 6-2 6-2 triumph. Can she repeat that achievement? Williams will be desperate for revenge.

Muguruza was waiting in the corridor for quite a while before Williams arrived, but both players are on the court now. The roof will be open for this match, which does seem to take away from the atmosphere slightly. I'm sure the tennis can make up for it.

It's very intense at the coin toss. Williams doesn't even look at the umpire on Muguruza as she elects to serve first. Muguruza is all smiles for the picture with the mascot, but it's game face time for the world number one. We're just a few minutes away from the start of this match.

Here we go then. We're ready for this match to get underway. Serena to serve first...

Incredible point to start the game. Williams charges to the net, and stretches to get the most unlikely of volley to drop over the net after Muguruza attempted the pass. A big serve hands Williams another point before Muguruza makes it 30-15. A double fault opens the door slightly, but Williams hits back with an ace before taking the opener.

Muguruza proves that she can be powerful too with a big first serve straight at Williams. Some good movement around the court gets the Spaniard into a position to take the next point. Williams is looking to dominate rallies, but she's off target with a forehand which drifts long. A weak second serve allows Williams to step forward to unleash a stunning forehand winner. It can't stop Muguruza from holding though.

The serving is excellent as Williams races to 40-0 without giving her rival a sniff. Muguruza attempts to get on top of a second serve, and the results are excellent as she sends Williams the wrong way with a forehand. "Shot," responds Williams. You can't argue with that. A lob in the next rally looks to put Muguruza in trouble, but she retreats to execute the perfect smash. However, an ace hands the game to Williams.

Too good from Williams. Another second serve is picked off, this time with the backhand. Muguruza needs to keep her first serve percentage high. A venture into the net ends with Muguruza hitting wide to give Williams a chance. How do you respond? An ace, of course. A couple of fly-overs in the past few minutes have distracted the players. If you didn't know, it's Australia Day, so we could have fireworks causing problems later on. A couple of errors from Williams allow Muguruza to move 40-30 up, and an excellent forehand winner makes it 2-2.

BREAK! Lovely tennis on show as Muguruza sends a forehand into the corner before taking the point with a simple volley. The Williams camp don't look pleased when a double fault is followed by Muguruza firing a backhand winner past the world number one. It's three break points to the Spaniard. Ace! That's one gone, but Muguruza doesn't need all three. A superb forehand down the line hands her the breakthrough.

These planes just won't go away. It must be distracting the players. Muguruza gifts Williams a point with a wild backhand which drifts long. The umpire steps in to call the ball out in the next rally, and Williams, who rarely challenges, doesn't ask for the technology. They exchange points once again, and we hear a first "come on" from Williams. However, a double fault brings up break point. Muguruza is almost on her knee to force deuce with a backhand which clips the line. She needs to produce some magic again to save break point with a perfectly constructed rally which ends with Williams finding the net. The quality is very high. Muguruza takes advantage, but Williams responds with a forehand winner off the second serve. A similar effort produces a third break point. She misses the chance to convert again, and Muguruza eventually capitalises to hold with another winner. That could be a crucial hold.

Just as Williams was doing earlier, Muguruza is dominating against the second serve. Another powerful winner makes it 15-15 early in the game. Williams hits back with an ace, before losing another point on the second serve. Another ace follows, as does a Williams error. Deuce. Incredibly, it's Muguruza who is taking charge in the longer rallies. Williams struggles to deal with the power of Muguruza's ground strokes, and the Spaniard has a break point. She won't stop there. Williams, on the stretch, hits a forehand wide. Muguruza has a double break.

UPDATE: Garcia-Lopez was serving for the opening set, but he failed to take advantage and Wawrinka has edged ahead with success in the tie-break.

SET! Much better from Williams. She reads the serve perfectly throughout the game, and the American suddenly has three break points thanks to an unstoppable return with the forehand. Muguruza hits back with a forehand winner of her own, and a wayward stroke from Williams makes it 30-40. Ace! What a time to deliver one of those. Not only does Muguruza save three break points, but she wins the next two points to take the opener. Are we heading for another shock?

Williams get onto the front foot for once in a longer rally, and Muguruza can't return a powerful stroke down the line. The Spaniard just needs to keep being aggressive. It's clearly her best chance of winning this match. Stunning return winners help, too, as Muguruza delights the crowd to get on the board in the second set. Williams has surely never been out-powered like this. It's a good hold for Williams though thanks to an ace. Can Muguruza continue to handle the pressure on serve?

BREAK! Williams is furious with herself when she sends a backhand long. Muguruza is similarly frustrated as she hits a simple volley too hard. A shout of approval from Williams follows a rally when she finally seemed to be dictating the tempo. Muguruza then misses the line by about an inch to gift her opponent two break points. The Spaniard responds by wrong-footing the top seed with a superb backhand, but she hits a forehand long to give Williams the game. Was that the turning point?

Great use of the full court again from Muguruza as she finds the corner with a forehand, before seeing Williams go wide with a wild ground stroke. The second serve just hasn't been good enough, and Muguruza cashes in to set up three break points by unleashing another winner with the forehand. Williams saves one with an ace, but she hits the net moments later as Muguruza immediately breaks back. Superb work from the 24th seed.

Williams appears to have a word with herself for a couple of moments after finding the net while attacking a second serve. She just hasn't found the rhythm to match Muguruza. A superb forehand winner may help her kick on. Muguruza races forward to meet a forehand which drifts just wide, but she hits the perfect spot from a similar position moments later. 30-30. Muguruza trips at the back of the court at the end of a rally which goes the way of Williams, who takes a few seconds to check on her rival. She's back up to serve an ace. Another break point arrives, but Williams is left frustrated after hammering a backhand into the net. Muguruza won't let her recover from mistakes like that. She's still bossing the rallies. It's a crucial hold.

This is the Williams you expect to see. She dictates the tempo of rallies much better in the game, and a couple of ground strokes are too much for Muguruza. The excellent defence is on show too as she chases down what appears to be a lost cause to force Muguruza into a difficult volley, which drifts long. A hold to love should give her confidence.

The moments we expect to see Williams come out on top are going Muguruza's way, and that doesn't happen too often. In truth, Williams hasn't been that poor, but it seems like she's been shocked by Muguruza's approach. At 30-15, we're treated to a rarity - a Williams challenge. It's a good one, too, as hawkeye shows a Muguruza forehand drifted long. Muguruza appears to make the wrong decision when a drive volley is returned, but she responds with a forehand which clips the baseline. Muguruza just refuses to be beaten in the longer rallies. Williams blinks first with a long backhand, and the game goes to Muguruza.

UPDATE: Wawrinka is one set away from another quarter-final appearance. The defending champion now leads Garcia-Lopez 7-6 6-4.

Excellent work from Williams, who breezes through a service game to hold to love and put the pressure back on Muguruza.

BREAK! Muguruza has risen to every challenge so far, but a double fault puts her in some trouble at 0-30. There's only one way to hit back. A fast unreturned serve. Williams responds well to come forward and find two break points with a forehand winner. Muguruza hits the net, and Williams will now serve for the second set.

Brilliant. Williams doesn't give Muguruza a chance of staying in the set. Three aces and an unreturned serve down the middle bring the world number one level. We're heading into a deciding set. What a match.

Williams delivers a perfect forehand winner, before seeing Muguruza draw level. The second serve looks vulnerable again as Williams gets her rival moving with a backhand down the line, and the Spaniard can't find the target with a return. It's two break points when Muguruza sends a forehand into the stands. Williams comes to the net, but the second volley finds the net. 30-40. The first serve at the body puts Williams into an awkward position, and she goes wide with the return. A scream follows when the next return drifts wide, too. Muguruza finds advantage twice, but she gifts Williams another break point. It's wasted again as a backhand strikes the net! Muguruza certainly isn't playing as well, but she holds, and that's all that matters in the decider.

Muguruza cuts a rally short to challenge when a Williams forehand appears to go long. It's a bad decision. The ball clipped the line. There's a few worrying moments for Williams as she struggles to catch her breath after a few seconds of coughing. Muguruza latches onto a second serve with a fantastic forehand winner. Another poor second serve is punished. The door is open to Muguruza. It's kicked open by a double fault. Two break points. Oh dear. Muguruza has a great chance to volley into the open court after sending Williams wide, but a poor shot sends the ball long. Williams gets a big serve in to force deuce, but the second serve is the problem as Muguruza gets on top of another to bring up a third break point. Williams defends impressively to bring the mistake from Muguruza in the next rally. The defence gets even better as Williams reaches a backhand on the stretch to leave Muguruza helpless and the crowd amazed. Muguruza hits three shots at Williams, who reacts impressively at the net, but the Spaniard eventually finds the gap to get back to deuce. The ace hands Williams advantage again, but the response from Muguruza is brilliant. Two fine volleys arrive with what really are needless screams from Williams, but Muguruza keeps her composure to hit the line with an excellent forehand. The drama keeps coming. A double fault hands Muguruza another break point before an ace immediately takes it away. Another break point arrives, but the big first serve digs the top seed out of trouble again. Fancy a sixth chance Garbine? She gets one, but once again she fails to convert as a backhand strikes the net. A marathon game eventually comes to and end. Williams holds. Will Muguruza regret those missed chances?

We're starting to see a much more animated Williams as she punches the air in delight after a brilliant forehand winner off the serve early in the game. Another winner follows to put the pressure on Muguruza, who hands her rival two break points with a wild forehand. It's another error which hands the game to Williams. Is there any stopping the world number one now?

The tide has certainly turned. Muguruza is struggling to cause the same problems for Williams, who shows that her serve is improving by firing down a couple of aces. It's a comfortable hold, and that's exactly what the American needs now.

It looks like Muguruza has found the line, and she appears to celebrate, but the point goes to Williams. The Spaniard responds impressively to boss the next couple of rallies, and her third ace makes it 40-15. She secures the hold with a superb forehand winner. Much better from the 24th seed.

Some great defence manages to keep Muguruza for much longer than should be possible, but Williams keeps her eye on drive volley to take the point. The response is emphatic as Muguruza meets the drop with a fine passing forehand. It's the only bright moment in the game for her though. Williams finishes the hold off with the ace. She's getting better with every game that passes.

UPDATE: It looked like one match was almost over, but Garcia-Lopez has come from a break behind in the third set to reduce the deficit against Wawrinka. Can he force the defending champion into a decider?

BREAK! Muguruza is still fighting, but Williams is finding the right areas with the best shots now. A gripping exchanges at 30-15 ends with the world number one coming forward to hit the backhand winner. Muguruza then finds the net to give her rival a break point. The first chance is wasted, but a forehand winner off the second serve earns Williams another opportunity. Ace! Much better from Muguruza, but she opens the door to Williams again with a backhand into the net. Williams finally takes the gift when a forehand from Muguruza drifts long. She'll now serve for the match.

It's a mixed bag at the start of the game. An unreturned serve from Williams is followed by a double fault, before Muguruza goes long with a wild forehand return. The ace brings up two match points. No more responses from Muguruza! A forehand drifts out and Williams raises her arm in celebration. It's bee a battle, but Williams is through to the last eight.

You have to feel for Muguruza. Some may have expected her to be blown away, but the Spaniard performed impressively and she looked the favourite at one stage. However, Williams improved when Muguruza's standards eventually dropped, and she pulled clear in the decider. It's job done for Williams, who will play Dominika Cibulkova in the next round.

#Serena flings her arms in the air as she overcomes an impressive #Muguruza 2-6 6-3 6-2 to reach her 8th #ausopen QF pic.twitter.com/Cr5AeyRVxy — Australian Open (@AustralianOpen) January 26, 2015

You can now read Darren Plant's full report of the win for Serena Williams over Garbine Muguruza. Two matches have been completed today, and they've both been thrillers.

After dropping the opening set to Muguruza, Williams looked to be heading for an early exit but after eventually prevailing in three sets, the world number one has revealed that keeping her focus during her opponent's onslaught was key to her earning a place in the quarter-finals.

Over on Margaret Court Arena, Stanislas Wawrinka and Guillermo Garcia-Lopez are currently locked at 5-5 in the fourth set, with Wawrinka currently possessing a two-sets-to-one advantage. The defending champion is certainly having to work hard to try to seal his passage through to the last eight.

Over on Rod Laver, David Ferrer and Kei Nishikori have made their way out onto court for their last-16 encounter. We've already seen two quality encounters on the number one show court in Melbourne - I'd say that there is a fair chance we will see a third.

RESULT! He made hard work of it in the end but Stanislas Wawrinka has finally booked his place in the quarter-finals with a four-set victory over Guillermo Garcia-Lopez. The Swiss had to save five set points in the fourth set to avoid being taken to a decider.

SET! Kei Nishikori has taken the first set against David Ferrer. In a battle of two tireless workers, it's the fifth seed who leads after winning the opener 6-3.

Milos Raonic and Feliciano Lopez are underway on the Hisense Arena. It's a match which could be won by returns of serve. Raonic has been in impressive form throughout the tournament, but veteran Spaniard Lopez has the game to frustrate anyone on tour.

UPDATE: Nishikori is a step closer to reaching the quarter-finals after taking the second set 6-3 to open up a 2-0 lead over Ferrer, while a break in the 10th game has handed the opener to Raonic in his match against Lopez.

If you've missed any of the results or news from day eight at the Australian Open, check out our dedicated page for the first Grand Slam of the year. The action has been very entertaining once again, but there's still plenty of tennis to be played.

Venus Williams is set to begin her fourth-round clash against Agieszka Radwanska at around 8am, while Novak Djokovic will meet Gilles Muller in the final match of the day.

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RESULT! Nishikori's hunt for a first Grand Slam title continues. The fifth seed has completed a 6-3 6-3 6-3 victory over David Ferrer to reach the last eight in Melbourne for just the second time. Read the full report of the match now.

SET! We predicted that the Raonic vs. Lopez match could be a tight contest, and the two players looked to have settled in for a long shift at the office. Lopez has just taken the set 6-4 to put pressure on Raonic. They're level now, but who will strike next?

SET! Raonic is back in front. The Canadian takes the third set 6-3 to leave Lopez with a mountain to climb.

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Serena Williams had to come from a set down to book her spot in the last eight, and the world number one admits that she needed to play her best match of the tournament so far to see off Garbine Muguruza.

The evening session is just getting underway on the Rod Laver Arena. First up, it's former champion Venus Williams against Agnieszka Radwanska, who is yet to drop a set at this tournament. They'll be followed by Novak Djokovic against Gilles Muller.

Tomorrow, Britain's Andy Murray will be hoping that he can end the run of Australian teenager Nick Kyrgios when they meet in the quarter-finals. The Australian admits that reaching the last eight at his home Grand Slam has been "crazy".

Last year's beaten finalist Dominika Cibulkova is enjoying another strong run in Melbourne, knocking two-time champion Victoria Azarenka out to reach the quarter-finals. The Slovakian says that she needed to play an "extremely good match" to beat the Belarusian.

As we've already touched on, Serena Williams dropped the opening set in her match against Garbine Muguruza, before coming back to win it in three. The top seed says that the support of the crowd really helped her turn the match around.

Defending champion Stanislas Wawrinka continued to quietly make his way through the draw earlier, beating Guillermo Garcia-Lopez in four sets. He'll face the man that knocked him out of the US Open next, Kei Nishikori. He admits that the Japanese star is a "great shot-maker".

Three-time finalist Andy Murray has been speaking ahead of his quarter-final clash with Nick Kyrgios tomorrow. He believes that his opponent needs to learn to deal with the weight of expectation, having become the first Australian to reach the last eight at his home Grand Slam since 2005.

SET! Feliciano Lopez and Milos Raonic are heading into a deciding set after the Spaniard beat the eighth seed in a tiebreak in the fourth set.

Here's some more from Murray ahead of his last-eight meeting with Nick Kyrgios. The Brit is naturally expecting the crowd to be behind the Australian teenager, but he admits that he is relishing the "big-match atmosphere".

Kei Nishikori is the fifth set in the men's draw, having moved into the top 10 in the world rankings last year. The 25-year-old admits that that is something he is still getting used to.

Feliciano Lopez continues to battle with eighth seed Milos Raonic in the fifth set on the Hisense Arena. When Lopez faced Andy Murray at Wimbledon a few years ago, his mother nicknamed the Spaniard 'Deliciano', and it would appear Britain's Fed Cup captain still has something of a soft spot for the 12th seed:

Vamos Deliciano.........#ausopen.

— judy murray (@judmoo) January 26, 2015

SET! Agnieszka Radwanska has dropped a set for the first time in this tournament, as Venus Williams makes the most of some below-par serving from the Pole to wrap up the opening set 6-3.
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RESULT! It's bad news for Judy Murray and the rest of the Feliciano Lopez fan club, the 12th seed is out. Milos Raonic has come through in five sets to clinch a spot in the quarter-finals, where he will face either world number one Novak Djokovic or Gilles Muller.

If you want to read more about Milos Raonic's hard-fought match against Feliciano Lopez, you can find our match report here. The eighth seed has never reached the quarter-finals in Melbourne before.
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American teenager Madison Keys will play in a quarter-final at a Grand Slam for the first time later this week after beating Madison Brengle earlier. The 19-year-old admits that she found it difficult to play against her friend and compatriot.

If you missed yesterday's action, including Andy Murray's win over Grigor Dimitrov, and Eugenie Bouchard setting up a quarter-final against Maria Sharapova, then you now watch the highlights here.

SET! Venus Williams and Agnieszka Radwanska will need a deciding set as the sixth seed has leveled the match, winning the second set 6-2.
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One of the matches of the men's quarter-finals should be the clash between fifth seed Kei Nishikori and defending champion Stanislas Wawrinka. The Japanese player admits that he is expecting an "exciting" clash.

Victoria Azarenka's comeback from injury ended with a fourth-round defeat to Dominika Cibulkova earlier. Despite the two-time champion losing, she's taken to Twitter to thank her fans for their support.

Venus Williams is closing in on a spot in a Grand Slam quarter-final for the first time in almost five years:

#Venus pulls out a crucial hold to edge 4-1 ahead. She's now just 2 games from a 1st Slam QF since the 2010 US Open pic.twitter.com/E7egOqg3qP — Australian Open (@AustralianOpen) January 26, 2015

RESULT! She's done it! Venus Williams is into the last eight after holding her nerve to serve out for a three-sets win over sixth seed Agnieszka Radwanska. She'll face teenager Madison Keys in the quarter-finals, with the prospect of a semi-final against sister Serena if she can continue her run.
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We're going to be focusing on the next match on the Rod Laver Arena, as top seed Novak Djokovic will be attempting to claim the final place in the quarter-finals when he faces Gilles Muller of Luxembourg in a few minutes. The winner of this match faces a tricky tie against eighth seed Milos Raonic next.

Djokovic's achievement, particularly at the Australian Open, are well-documented. The world number one has seven Grand Slam titles to his name, four of which have been won in Melbourne. He hasn't missed out on a place in the last eight since 2007, and every time he's got beyond the quarter-finals he's gone on to win the event.

Muller's history at this tournament is somewhat more modest. The 31-year-old has never reached the fourth round before. In fact, he's only made it past round two once before this year. His best Grand Slam performance came at the 2008 US Open, where he reached the quarter-finals, where he was beaten by eventual champion Roger Federer.

Muller has made a good start to 2015, he matched his career-high ranking of 42 coming into this event, and will climb higher again when the new rankings are published next week. He's also coached by former British tennis player Jamie Delgado.

The players are on court warming up ahead of their match. This will be the first time that these two players have ever faced each other, despite being on the tour together for 12 years.

The duo are ready to go, with Muller serving first.

Djokovic tries to put some pressure on his opponent straight away, firing a forehand winner down the court before Muller hits his backhand into the net. An ace gets the world number 42 back into the game, and he seals it with a forehand down the line.

Muller can't return Djokovic's first serve, and the world number one hits an ace two points later as he races to a 40-0 lead. Muller gets off the mark with a big return, forcing a mistake from Djokovic, but he top seed seals it with another ace.

Muller tries too hard with a forehand from the baseline, and slices it well long. The unseeded player finds a big serve to force a backhand error from Djokovic on the next point though, before blasting a forehand past the world number one. Muller has made a decent start on serve in this match.

Feliciano Lopez could have been the next opponent for the winner of this match, but he lost a deciding set against Milos Raonic earlier. The Spaniard insists that he is happy with his run at the Australian Open despite the defeat.

There was some British success in the men's doubles earlier as Dominic Inglot and Romanian partner Florin Mergea knocked top seeds Mike and Bob Bryan out. The Brit reveals that aggression was key.

It's another comfortable hold of serve for Djokovic. The top seed's serve is a bit too much for his opponent at the moment as Muller misses a run of returns, although a wayward backhand from Djokovic gives him a point midway through the game. The Serb seals it with a serve out wide though.

Muller might not be testing the Djokovic serve yet, but he's looking increasingly comfortable during his own service games. He keeps Djokovic off the board, picking up the edges of the court with some powerful deliveries to force four out returns in a row from the world number one.

There's not been a sniff of a break point yet, and that continues as Djokovic eases to another game as Muller misses a couple of returns before the four-time champion blasts an ace down the middle of the court.

BREAK! Muller is under pressure as Djokovic sprints around behind the baseline to fire two stunning forehands past him for a 30-0 lead. In a rally, Muller undercooks a forehand, slicing it into the net to give the world number one three break points. Muller comes into the net, and it forces a mistake from the Serb as he fires a looping forehand just wide. A long forehand gives Djokovic the break on the next points though.

Djokovic has to work to consolidate the break, but he manages to keep his serve intact. Muller hits some solid forehand to get the game to 30-30, but a slices backhand from the top seed followed by a long backhand return from the world number 42 allow Djokovic to escape.

Muller serves well to leave Djokovic having to try to serve the set out next. The Luxembourg player mixes it up a bit, coming into the net for a couple of volleys, before clinching the game with an ace.

Djokovic has called the trainer onto the court as he's injured his hand. It looks like he's grazed a couple of knuckles on his right hand while slipping to change direction behind the baseline.

Once he has his fingers bandaged, Djokovic will be serving for the set, and looked at the stats so far, it should be comfortable for the Serb:

#Djokovic to serve 5-4 1st set v #Muller. Gilles only won 4/9 (44%) 2nd serve pts s far. Nole on it. #ausopen pic.twitter.com/E8AIW8UsqF

— Australian Open (@AustralianOpen) January 26, 2015

SET! The hand injury doesn't seem to have caused much of a problem for Djokovic as he breezes through another service game to take the first set after just over half an hour on court. A volley brings up three set points, but he needs just the one as Muller hits his forehand long.

It looks like Muller is going to start the second set with a relatively straight-forward service game, but Djokovic produces a superb backhand to keep himself in the game. Muller halts any hopes of an early break for the top seed though, wrapping it up with a powerful forehand inside the baseline.

Djokovic races to a 40-15 lead, firing another ace down the middle of the court, but he's made to work for the game as Muller catches him out in the next point with a well-struck backhand return. The world number 42 can't return his next serve though, keeping the set on serve.

Muller is certainly not giving anything away on serve, as he fires some more booming deliveries down the court at the world number one. The top seed misses a series of returns, and challenges when a forehand is called wide, but hawkeye confirms that it was a fraction out, giving Muller a hold to love.

At 40-0 down, Muller tries some ambitious shots to try and keep himself in the game. He gets caught at the net, but sprints back to the baseline before going for an overhead forehand, but Djokovic smashes it straight back. The unseeded Luxembourg player gets his racquet to the ball, but his forehand is wide.

Muller misses a forehand on the opening point, but Djokovic tries to hard to try and force a chance for a break, blasting a series of returns long, before handing Muller the game with a wayward forehand.

Muller mixes up his shots from the baseline, and he forces an error at the net from Djokovic to edge ahead, but the top seed makes amends with a stunning overhead smash on the next point. A wide backhand from the world number 42 leaves Djokovic just a point from sealing the game, which his does with another smash. That's the first time Muller has really looked like he could test the Djokovic serve, but the world number one upped his game.

Djokovic is on the attack, pressuring his opponent into a couple of mistakes to bring up deuce. The top seed has a chance to break when he powers a forehand volley past his opponent, but Muller saves it before clinching the game with an ace. That was a superb response to save the break from the world number 42.

Djokovic makes the first double fault of the match, but recovers well with a forehand to the back corner. Muller tries to catch Djokovic out with a cross-court backhand, but the slices shot doesn't quite clear the net.

Djokovic has been on the attack a bit more during the last couple of Muller service games, and he gets the first two points in this game, but Muller responds with some big serving to level, before he gets the benefit or a lucky strike on the net chord, before a long Djokovic return hands him the game. The world number one has to serve to stay in the set next.

The match on the Rod Laver Arena before this one so Venus Williams make it through to the quarter-finals. The four-time champion reveals that sister Serena is her inspiration.

Speaking of Serena, you can now watch highlights of her round four win over Garbine Muguruza earlier, which sets up a quarter-final against 2014 runner-up Dominika Cibulkova.

Djokovic has no problems keeping himself in the set as Muller gets just a single return in, but a sloppy backhand with his next shot still gives Djokovic the point as the world number one gets the hold to love. It looks like this set could be heading for a tiebreaker.

BREAK! Djokovic is still looking for the break, taking a 30-0 lead again, but once again Muller gets back on level terms with some superb serving, including a bold second serve to the top seed's body. He mis-cues a volley though to give Djokovic a break point, although the world number one fails to convert with an overhit backhand. He saves another break point with an ace down the middle of the court. The errors return for Muller though as he misses two backhands in a row to hand Djokovic the break, and leave the four-time champions serving for a two-set lead next.

SET! Djokovic quickly brings up three sets points, as Muller struggles with his returns again. The world number 42 saves the first with a punchy forehand, but his return is long on the next point to hand Djokovic the set.
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There's been a bit of an embarrassing discovery for the organisers of the tournament this morning as they officially opened the recently renovated Margaret Court Arena. Unfortunately, the roof leaked, despite £100m having being spent on the facility.

Muller is still looking as determined as ever during his own service games, coming inside the baseline for a volley before hitting a couple of forehand winners past the top seed to start the third set with a comfortable hold.

Djokovic is keen to get another look at the Muller serve as quickly as possible as he fires three aces past the world number 42 on his way to a swift hold.

Djokovic has a chance to get a break on the board early in this third set as Muller gets a volley all wrong. The world number one misses a forehand though, letting Muller off the hook, and the Luxembourg player keep the set on serve with a volley followed by a big serve. Even if Djokovic ends up winning this match in straight sets, it won't have been an easy night's for work the top seed.

Djokovic continues to race through his own service games, forcing a string of missed returns from Muller after opening with a well-timed forehand winner.

Muller appears to be on his way to a comfortable hold, following a forehand volley with back-to-back aces, but Djokovic gest back into the game with a couple of well-placed backhands. The world number 42 ups his game though, and sees it out with his third ace of the game.

For the first time in this match, Gilles Muller has break points against the Djokovic serve as the blasts a forehand winner down the line. The world number one serves big to force a long return from his opponent before Muller looks for the sideline, but slices a backhand just wide to take the game to deuce. Djokovic has another break point to save moments later, but he finds the baseline with an aggressive forehand. He forces advantage, and somehow manages to get the better of Muller with a lively exchange, culminating with a sliced backhand after sprinting in from the net.

After a slightly off game, Djokovic seems to have rediscovered his intensity as he pushes for a break. Muller gets the better of him with a superb drop shot, before a forehand at 30-30 allows him to edge ahead, and he takes the game when Djokovic fires long on the return.

A double fault from the top seed gives Muller the lead, but Djokovic levels it up with an ace before a long forehand puts the Serb ahead, and he fires another ace down the middle to see it out. This has been a closely-contested set, with both players surviving difficult service games, and neither securing a break yet.

Djokovic has a chance to break to leave himself serving for the match next, but Muller saves the break point with a powerful volley, before a big serve forces a long return from the Serb, allowing Muller to come in to the net again on the next point for another volley. Muller has shown some good variety at the net in this match, and it's caused a few problems for the top seed.

As Venus Williams prepares for her first Grand Slam quarter-final in five years, the 34-year-old hopes that this will be the start of a consistent run for her.

Nick Kyrgios takes on Andy Murray tomorrow in a big to reach a Grand Slam semi-final for the first time. The 19-year-old is also a big basketball fan, so Golden State Warriors' star, and fellow Australian, Andrew Bogut has sent him a good luck message:

Nick Kyrgios, Keep being yourself. The tall poppy pc bridgade can build a bridge. Best of luck in the next round. — Andrew Bogut (@andrewbogut) January 26, 2015

It's still level in the highly-competitive third set as Djokovic survives another tricky game. A double fault keeps the game level, but an ace from the world number one gives him a 40-30 lead, and he takes the game on the next point when Muller misses the return.

Serena Williams was in the crowd earlier to watch her sister make it through to the last eight. She spoke last week of how inspired she had been by Venus's return to form, and she's tweeted her support again this lunchtime:

Sooo proud of you Vee @venuseswilliams love u — Serena Williams (@serenawilliams) January 26, 2015

BREAK! Djokovic looks desperate to avoid the lottery of a tiebreak as he races to a 40-15 lead, but Muller gets to deuce with a stunning overhead smash. The world number one has a chance to break though, picking out the back corner with a forehand down the line, and a cross-court backhand gives him the game. He'll be serving for the match next.

Here's some more from Venus Williams as she heads into the quarter-finals. The 18th seed is determined to keep her focus going into a last-eight match at a Grand Slam for the first time since 2010. If she can beat Madison Keys, there's a chance she'll play her sister in the semis.

GAME, SET & MATCH! Djokovic eases to a 40-0 love lead with some superb serves before Muller slices a forehand into the net.

It wasn't an easy match, but Djokovic managed to raise his level just at the right time to see out the match. Next up, it's a tricky tie against Canada's Milos Raonic for the top seed.

Djokovic is complimentary about his opponent about while speaking on court at the end of the match: "He deserves a lot of respect, I was fortunate to serve very well at the important moments. He's got an exceptional slice serve, comes to the net and has a lot of variety in his game."

When asked about facing Raonic in the next round, Djokovic says: "The next one is one of the top three servers on the tour next to Karlovic and Isner. We're good friends, we speak the game language, we've known each other quite a few years. He's one of the new generation, future stars that are coming through. I guess I'm going to need to return better than I did tonight."

If you want to recap the match, our report of Djokovic's straight-sets win over Gilles Muller is now online.

Well that's it from day eight in Melbourne. There was success for both of the top seeds today, while Venus Williams, Milos Raonic and Kei Nishikori are all safely through. Don't forget to join us again from midnight for the start of the quarter-finals with Andy Murray's highly-anticipated match against Nick Kyrgios scheduled for tomorrow, as well as Maria Sharapova's match against Eugenie Bouchard. Until then, thanks for joining us today, goodbye.
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