Arsenal lost for the second time in this season's Champions League after suffering a 3-2 defeat to Olympiacos at the Emirates.
The Greek champions took the lead through Felipe Pardo's deflected strike, before Theo Walcott levelled the scores.
An own goal from David Ospina saw the Gunners slip behind again, but Alexis Sanchez headed in to equalise after the break.
However, within a minute of drawing level, Alfred Finnbogason turned home Pardo's cross, to leave Arsenal staring at an early exit from the competition.
Find out how the action unfolded below.
Hello everyone! It's the second matchday of this season's Champions League and there are some cracking games taking place across Europe this evening. Here, our focus will be on two teams who made poor starts to their group stage campaigns, as Arsenal welcome Greek champions Olympiacos to the Emirates.
The scene is set at Emirates Stadium. Who will be @Arsenal's key man tonight? #AFCvOLY pic.twitter.com/KbYQyO9oto
— Arsenal FC (@Arsenal) September 29, 2015
The Gunners will be looking to bounce back from a 2-1 defeat to Dinamo Zagreb in their last European outing. They produced a poor display in Croatia that evening and finished the night with 10 men, but they will come into today's match off the back of a 5-2 victory over Leicester City at the weekend.
Meanwhile, Olympiacos were also beaten in their first group match of this year's competition. The Greek outfit were outplayed and fell to a 3-0 defeat against Bayern Munich and will be hoping that they can pull of a shock in London tonight to get their campaign back on track.
Arsene Wenger made plenty of changes to his side for the trip to Zagreb and it ended up costing the Gunners dearly. Let's see if the Arsenal boss has made any alterations to the starting lineup this evening, as the teams news is in.
ARSENAl XI: Ospina, Bellerin, Koscielny, Gabriel, Gibbs, Coquelin, Cazorla, Oxlade-Chamberlain, Ozil, Sanchez, Walcott
OLYMPIACOS XI: Roberto, Masuaku, Siovas, Costa, Elabdellaoui, Cambiasso, Kasami, Pardo, Dominguez, Seba, Ideye
ARSENAL SUBS: Cech, Mertesacker, Debuchy, Monreal, Chambers, Ramsey, Campbell
OLYMPIACOS SUBS: Kapino, Masuaku, Vouros, Dominguez, Finnbogason, Pulido, Hernani
As you can see, Arsenal have made some changes to their side, with David Ospina coming in to replace Peter Cech in goal once again. There are two other switches in the defence, as Gabriel returns for the first time since his red card at Chelsea, while Kieran Gibbs replaces Nacho Monreal at left-back.
In the midfield there is also a welcome return for Francis Coquelin, who has missed the last two games with a knee injury. He will be joined by Santi Cazorla in the centre of the pitch, while Theo Walcott continues to lead the attack with Olivier Giroud missing out through suspension.
Meanwhile, former West Brom striker Brown Ideye will lead the line for the visitors. Kostas Fortounis, Felipe Pardo and Seba will all provide the support in the attack, while there is also a start in the centre of the midfield for Esteban Cambiasso, who spent last season at Leicester.
So, Arsenal will be looking to pick up their first points in this season's Champions League, after a truly miserable start to their European campaign in Croatia. They had been expected to claim a win against Dinamo Zagreb two weeks ago, but things did not go according to plan for Arsene Wenger's side.
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The Gunners had hit the woodwork twice early on, but found themselves behind when Alex Oxlade-Chamberlain turned the ball into his own net. Olivier Giroud was then sent off for picking up two cheap bookings, before Junior Fernandes headed in to give the hosts a two-goal lead.
Although Theo Walcott pulled a goal back late on for the Gunners, they were unable to score again as their opponents won for the first time in the group stages of the tournament for 16 years. It led to a barrage of criticism for the club, with Wenger receiving plenty of stick for making a number of changes to his side and resting key players.
They were beaten again three days later in a heated clash against Chelsea, but since that match at Stamford Bridge they have claimed two wins. They bounced back to form by beating rivals Tottenham in the League Cup, before they came from behind to earn a 5-2 win over Leicester in a thrilling match at the weekend.
Alexis Sanchez bagged a hat-trick in that clash at the King Power Stadium to end his barren goal drought. Theo Walcott and Olivier Giroud also found the net, as the Gunners doubled their tally in the league for the season.
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Making the trip to the Emirates this evening are an Olympiacos side who have made a superb start to their domestic season. They are currently top of the Superleague after winning their opening five games and they are firm favourites to win a sixth title in a row.
The club have actually won 17 of the past 19 titles in Greece and are by far the most successful team in their country's history after winning a total of 42 championships. However, they have struggled to replicate that success in Europe and they have never made it beyond the quarter-finals of the Champions League.
Marco Silva's side have not made a good start to this season's tournament and they were beaten 3-0 by Bayern Munich on the opening matchday. Thomas Muller scored twice and Mario Gotze grabbed the other, as the Germans recorded a routine win at the Karaiskakis Stadium.
Olympiacos warmed up for tonight's match in similar fashion to Arsenal, as they romped to a 5-1 win against PAS Giannina. It has led Arsene Wenger to comment that the Greeks have a "big advantage" over the Gunners, as they are able to prepare more thoroughly for European games due to the lack of competition in their own league.
These teams have met in the group stage of the Champions League on six occasions in the past six seasons and the home side has always come out on top. Their last meeting at the Emirates came in October 2012, where goals from Laurent Koscielny, Gervinho and Aaron Ramsey helped the Gunners to a 3-1 victory.
We're just three minutes away from the start of the match and both teams are out at the Emirates. Don't forget that we have coverage of all the other group stage matches taking place across Europe this evening.
KICKOFF! We are underway at the Emirates!
As you would expect, the Gunners are seeing plenty of the ball in the early stages of the match. The visitors look happy to allow their opponents to pass it around just inside their half and they are getting lots of men back to defend.
Arsenal finally get in behind the Olympiacos defence with Walcott breaking clear down the left. The England international then holds the ball up and waits for runners to arrive in the middle, but when he whips in the cross Roberto spots the danger and comes to claim.
Sanchez shows a first glimpse of his skill when he comes in from the left and drives at the defence. He then ghosts past two players, before he is eventually brought down just outside the box, but the referee did not spot a foul as the visitors cleared the danger.
CHANCE! First big chance of the match for Arsenal as they break quickly from an Olympiacos corner and get plenty of men forward. Sanchez leads the charge with a powerful run, before he spots Oxlade-Chamberlian bursting into the box. The midfielder is at a slightly tight angle as he receives the ball, and tries to fire a strike past Roberto at the near post, but his effort ends up crashing into the side netting.
SAVE! The Gunners are looking a real threat on the counter attack and once again Sanchez is heavily involved. The Chilean breezes through the centre of the pitch and picks out Walcott, who cuts onto his left foot and drills in a low strike from just inside the box that is blocked by Roberto.
Sanchez seems fired up for the hosts this evening and he is all over the pitch right now. He also gets back to help his team deal with an Olympiacos attack, and it seems that his hat-trick at the weekend has provided a major boost of confidence to his overall play.
Olympiacos must be pleased at the way things have gone for them this evening, but they have been guilty of losing the ball in some dangerous areas. Arsenal have already shown the threat that they pose on the break, and they are sure to punish their opponents for any further lapses in concentration.
SHOT! The visitors are enjoying a good spell in the match and they put together a decent passing move that sees Fortounis pick the ball up just outside the box. The Greek international then looks to drive a low effort into the corner, but he doesn't catch the ball cleanly and his shot bobbles wide of the post.
It may be goalless here at the Emirates, but over in Germany Bayern are already 3-0 up against Dinamo Zagreb. A win for the Bavarians will lift them up to six points ahead of their double-header with the Gunners.
The way that Arsenal have started this match is reminiscent to their last-16 clash against Monaco last season. They began the game very cautiously and struggled to seriously test their opponents, before they were caught out and made to pay.
SHOT! Arsenal almost fall apart at the back as Koscielny and Gabriel fail to deal with a long ball that drops to Ideye. He then lays the ball off to Fortounis, who sees his strike from the edge of the box take a deflection and loop onto the roof of the net.
GOAL! Arsenal 0-1 Olympiacos (Felipe Pardo)
The Gunners are made to pay for their slow start to the evening as the visitors take a shock lead. Having just won the corner, Fortounis plays the set piece to Pardo on the edge of the box. The Colombian then fires in a drive that takes a big deflection off Oxlade-Chamberlain and ends up in the back of the net.
GOAL! Arsenal 1-1 Olympiacos (Theo Walcott)
Arsenal respond to falling behind in the best possible fashion by quickly getting back on level terms. Sanchez is the creator as he slides a great pass through to Walcott, who then cuts onto his right foot and keeps his composure to finish clinically past Roberto.
For long periods it seemed as if we wouldn't see a goal in this first half, but the match has sprung into life. The crowd have also begun to make some noise, as they have been very subdued up to this point.
GOAL! Arsenal 1-2 Olympiacos (David Ospina own goal)
Having just got themselves back into the match, Arsenal slip behind again, but it's a truly horrendous mistake by Ospina. The keeper comes to collect a corner from Fortounis, but he ends up carrying the ball backwards and drops it over his own line. It was a really poor piece of goalkeeping and once again the decision not to play Cech will be questioned.
YELLOW CARD! Sanchez picks up the first booking of the evening.
YELLOW CARD! It's another booking for the Gunners and this time Gabriel is shown yellow for a late challenge on Ideye.
There are going to be two minutes added on to the end of the first half.
HALF-TIME: Arsenal 1-2 Olympiacos
Well, that certainly wasn't in the script for the Gunners as they head into the break trailing. A shockingly bad goalkeeping error from David Ospina has given Olympiacos the lead and Arsenal's hopes of making it through to the last 16 are already in serious danger.
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Here's how the stats are looking after the opening 45 minutes in North London. Arsenal have seen a lot more of the ball than their opponents and have amassed 61% of the possession. However, they have only managed three attempts on goal, with Olympiacos registering four efforts and finding the net twice.
I updated you earlier about how Bayern Munich were getting on against Dinamo Zagreb, and the Germans have added another goal to lead 4-0 at the break. Robert Lewandowski has kept up his impressive goalscoring form with a double, while Mario Goetze and Douglas Costa have scored the other goals for the group leaders.
RESTART! Olympiacos take the kick off and get the second half started.
SUB! The visitors have made a change at the break, with Finnbogason coming on for Ideye.
Arsenal are already starting to show their frustration, as they crowd around the referee to complain about a free kick given against Oxlade-Chamberlain. The midfielder did seem to win the ball fairly, but the Gunners must feel that everything is going against them right now.
You just wonder when Wenger will look to his bench in this second half. Ozil may be one of the prime candidates to come off, as he has made little impact and is easily brushed off the ball again. However, they don't have too many options, with Campbell the only striker on the bench.
SHOT! The visitors are looking solid and Arsenal are struggling to find a way through. They also look a threat on the counter attack, and Kasami tries his luck from just outside the box with a fierce strike that is hit straight down the middle and is comfortably held by the keeper.
SUB! It's all going wrong for Arsenal this evening, as they lose Koscielny to what looks like a hamstring injury. Mertesacker is coming on to replace him at the back.
SUB! Arsenal are making another change, with Ramsey coming on for Coquelin.
OFF THE LINE! How have Arsenal not found the back of the net here? Bellerin is played through by Ramsey, and after seeing his initial cross blocked, he picks out Mertesacker in the middle. The German then sees his low effort kept out by Roberto, before Cazorla's shot from the follow up hits Elabdellaoui on the line.
SAVE! Arsenal have stepped it up a gear and they win a corner when Roberto tips Oxlade-Chamberlian's deflected cross over the bar. From the resulting set piece, the ball is played to Cazorla outside the box, and the Spaniard then fires in a powerful drive that is parried to safety by the keeper.
YELLOW CARD! Roberto is booked for time wasting.
GOAL! Arsenal 2-2 Olympiacos (Alexis Sanchez)
A goal has been coming and finally the Gunners get on the scoresheet in this second half. Walcott shows his skill down the right, before whipping in a great cross that is headed into the far corner by Sanchez.
GOAL! Arsenal 2-3 Olympiacos (Alfred Finnbogason)
Incredible scenes at the Emirates as Olympiacos score for a third time this evening. Cambiasso picks the ball up just outside the box, before sliding in Pardo down the right. He then whips in a low cross that Finnbogason gets a touch on to divert past Ospina and into the bottom corner.
Wenger must be furious at the way his team have cheaply given away a goal, and they were back on level terms for less than a minute. The defending from the Gunners has been poor all evening and it will take a big effort to equalise once more.
SUB! Olympiacos are making a second change of the evening, with Hernani taking Seba's place.
YELLOW CARD! Finnbogason goes into the referee's notebook for a foul on Cazorla.
YELLOW CARD! It's another card and this time Cambiasso sees yellow for handling the ball just outside the box. Arsenal have also been given a free kick in a very promising area, with Cazorla and Ozil standing over the ball.
SAVE! Ozil steps up to take the free kick and he curls in a fine strike that is headed for the corner, until Roberto flies across his line to push the ball wide.
YELLOW CARD! Ozil is shown a card for fouling Hernani, while Fortounis was booked for not retreating during the previous free kick.
Ramsey has played well since he has arrived on the pitch and once again he slides Bellerin through down the right. However, the Spaniard is quickly closed down by the Olympiacos defence, before Ramsey fires high over the bar from long range.
SHOT! Olympiacos have everyone behind the ball now and they give away another free kick in a good area for the Gunners. This time Ozil whips a cross into the middle, which is cleared to Oxlade-Chamberlain. The midfielder then sees his low drive deflect behind for a corner, but the Gunners are unable to make anything of the set piece as the Greeks survive.
CLOSE! He's already scored a great header this evening and Sanchez comes close to another when he flies in to meet a cross from Ramsey. However, his attempt takes a slight deflection and goes a few inches wide of the target.
SUB! Arsenal make their final change of the match, with Campbell coming on to replace Bellerin. The Costa Rican spent a season on loan at the Greek side and memorably scored against Manchester United.
SUB! Olympiacos also make their last substitution as Vouros comes on for Fortounis.
Cazorla almost finds the net when he whips in a free kick from the left that looks as if it will drop in the far corner. Roberto had read the situation well though, and the keeper is across to help touch the ball over the bar.
There are going to be at least four minutes of stoppage time. Will it be enough for Arsenal to salvage a point?
SHOT! Walcott uses his pace well to burst clear down the left, before he drives into the box. He then gets the ball onto his right foot and tries to shape an effort into the far corner, but his final attempt is poor and he drags the ball wide of the post.
The Gunners are throwing everything they have at Olympiacos, but the visitors are holding solid at the back. They are heading clear everything that is coming their way and time is almost up for Arsenal.
FULL-TIME: Arsenal 2-3 Olympiacos
Boos ring out around the Emirates as the referee blows the final whistle. It's Olympiacos who come away from North London with all three points, as Arsenal's miserable start to the Champions League continues. With two games to come against Bayern Munich, a place in the knockout stage looks an awfully long way away now for Arsene Wenger's side.
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Our coverage of tonight's match may be over, but we've got analysis and player ratings to come in just a bit. We've also got more Champions League action coming up tomorrow, as the group stage continues. Until then, goodbye!
