Novak Djokovic headed into today's ATP World Tour semi-final against Juan Martin Del Potro in imperious form, winning all three of his group matches in London.
Del Potro stunned the Serb with a strong start to take the opening set and put the world number one under serious pressure.
Djokovic responded magnificently to storm into tomorrow's final, taking the last two sets in a spirited comeback performance.
Read how a pulsating match unfolded with Sports Mole's minute-by-minute updates below.
Afternoon tennis fans, thanks for joining us at Sports Mole ahead of what promises to be an exciting semi-finals day at 02 Arena.
We've got four Grand Slam winners all vying for a place in Monday's final across two titanic battles. Later tonight its Andy Murray against his nemesis Roger Federer but first up its Juan Martin del Potro taking on Novak Djokovic.
Novak has been imperious this week, topping his group to stay on course for a £1.7m jackpot for staying unbeaten.
Del Potro beat Djokovic earlier this year in London, winning at Wimbledon to secure an Olympic bronze medal.
Djokovic has won their last two meetings but Del Potro is right back on form after beating Roger Federer in convincing fashion last night.
The world number one has benefited from an extra day's rest and is the clear favourite as the player's make their way to the court.
The 02 Arena creates an impressive atmosphere for this event, building the tournament into the showpiece occasion the standard of play deserves.
Coin toss completed, the formalities are out of the way. Djokovic has chosen to serve first, game on!
Novak will get us underway shortly, really interesting battle of Del Potro's raw power and the Serb's relentless style.
Del Potro is limbering up with that ferocious serve which will be undoubtedly be a weapon during the course of this match.
We're about to get underway, Djokovic to serve first.
Novak looks ready for a comfortable hold before making a pair of unforced errors. 40-30
Make that three errors for Djokovic, very strange to see mistakes like that from the world number one. Deuce.
Del Potro tries to apply pressure at deuce but hits a heavy forehand long to hand Djokovic the opening game.
An awesome point on Del Potro's serve. Djokovic performs minor miracles at the baseline to keep the rally alive before the Argentine swats aside a volley at the net to claim the point.
Djokovic steps up the intensity to earn two break points. Del Potro saves the first with a trademark serve then cracks a massive forehand down the line. Deuce.
That huge forehand was clocked at 94mph, a huge shot that has the crowd purring. Del Porto follows that up with a big serve but Novak hits back instantly for Deuce 2. High class stuff already from the in-form pair.
The big man responds well and uses his serve to close out his opening service game. Important early hold there for Del Porto.
Novak races to a 40-0 lead with a series of quality shots including a wonderful forehand winner.
Djokovic gets his first ace to bring up a comfortable hold. All to easy on serve for the world number one.
Djokovic has Del Potro moving all over the court, toying with the Argentine before wrapping up the point with a huge overhand smash. Del Potro responds with a 126mph serve to go 30-15 ahead.
Big hold for Del Potro as he matches a big serve to a strong forehand to tie the scores at 2-2.
Superb exchange at the net after a short lob from Djokovic. Del Potro responds with a brilliant backhand smash to make the score 30-15.
Del Potro fails to build momentum and launches a forehand into the net to keep the match on serve in the first set.
A succession of forehand missiles win Del Potro the opening point of his next service game. His raw power is frightening at times.
Del Potro mixes his game up to great effect, using a lovely drop shot to find Djokovic napping.
The Argentine has found his groove and earns his easiest hold of the match so far.
Djokovic responds quickly, using a wide serve to build a 40-15 lead but a pair of winners drift wide the for Serb to send us to Deuce.
A long rally eventually hands Djokovic the chance to gain advantage with an overhand smash but he can only launch the ball downward into the net. Break point Del Potro.
Unforced error from Del Potro lets the world number one off the hook. Back to deuce.
Del Potro lets Djokovic off the hook with a poor forehand. Novak seizes the initiative to earn the vital hold.
Del Potro uses the change of balls to smash a serve down the line and build a 40-15 lead on serve.
Comfortable hold for Del Potro and there's still nothing to choose between these two in the first set.
The Serb quickly cancels out an unforced error with a strong serve. Del Potro hits his best shot of the match in the next rally, unleashing a forehand winner on the run.
Del Potro punishes a poor second serve to earn two break points.
A huge moment in the first set as Del Potro forces another mistake from Djokovic to earn the break. He takes a 5-4 lead and will serve for the set.
The Argentine now needs to maintain his composure to close out the opening set. Big chance for Del Potro.
Another massive forehand down the line from Del Potro to take the first point.
Del Potro smashes a huge serve across court for his second ace and a 30-0 lead.
Another unforced error from an out of sorts Djokovic puts Del Potro 40-0 ahead.
The Argentine finishes the job with a smash at the net to take the first set. Thoroughly impressive stuff from Del Potro who deserves to lead.
Djokovic is back on serve and needs to find some form before this match disappears. Del Potro is right on form and wins the opening point with a delicate lob from the baseline.
Del Potro uses the lob to catch Djokovic off guard again. The Serb tries a trick shot but to no avail and he trails 15-40.
Djokovic is is big trouble straight away in the second set but fights back to deuce with a brilliant volley at the net.
A fifth ace gets Djokovic to game point but a poor forehand lets Del Potro off the hook. Back to deuce.
Del Potro earns a third break point of the game but fails to convert.
Chance missed for Del Potro as Novak hangs on to hold. Tough start to the second set for the out of sorts Serb.
Back on serve with Del Potro and the Argentine resumes normal service with a massive serve.
Spoke too soon there as Del Potro serves his first double fault of the match. He recovers to build a 40-30 lead.
Nice recovery from Del Potro as he continues to build momentum. We're all square and on serve early in the second set.
Shocking start in the next service game for Djokovic who continues to struggle on his forehand. A pair of errors quickly find the Serb 0-30 down.
Huge chance for Del Potro as he takes a 40-0 lead on Novak's serve. The first break point goes begging with a long forehand.
An unbelievable rally sees Del Potro earn the crucial break. He stays strong at the baseline and unleashes a corker of a forehand to leave Djokovic with no chance. That puts the Argentine a set and a break ahead.
That last rally was a 33-shot marathon but it was Djokovic who seemed to visibly tire which is surprising given all the talk about him having an extra day's rest.
Novak needs to find a response quickly or his season will be over. Del Potro has upped the intensity and must now be considered the favourite to progress.
Djokovic recovers to earn two break points of his own. Del Potro swats aside the first with a forehand winner and sends it to deuce with a monstrous 129mph serve.
Top-class tennis from Djokovic to earn a third break-point chance of the game.
A forehand goes long but Djokovic is unhappy with the call and uses a challenge to no avail. The ball is just out and we go back to deuce.
Another advantage for Djokovic after some sloppy play from Del Potro.
This time the Serb makes no mistake with his first break of the match. Back to 2-2 in the second set and could that be the catalyst for a Serbian revival?
Djokovic looks revitalised and races to a 30-0 lead back on serve.
A backhand up the line followed by a well-placed serve puts the Serb 3-2 ahead in the second set.
Del Potro responds on serve with a forehand winner clocked at 102mph, awesome stuff. That's followed up by a volley at the net to go 30-0 up.
Del Potro holds to level things up in the third set. He leads 6-4 3-3.
Djokovic smashes home a pair of winners to go 40-15 ahead on serve. He follows that up with a timely ace to re-take the lead in the second set.
Del Potro is back on serve but lets a forehand drift long to lose the opening point.
Djokovic keeps the ball in play consistently and forces a string of errors from the Argentine to earn two break-point chances.
Del Potro hangs on to take the game to 30-40 after a forehand winner hits the net for Novak.
Another big service return from Djokovic forces the mistake and puts the Serb firmly in control in this second set. Djokovic 4-6 5-3 Del Potro
Djokovic is now serving to win this second set and level the match.
Del Potro is fighting to respond and brings the game to 30-30. Pressure on!
Set Point to Djokovic after a poor return from Del Potro. The world number one makes no mistake and we are level at a set apiece.
A short break now before the deciding set begins. Del Potro had a chance to put this match away early in the second set but the relentless Djokovic responded brilliantly. All to play for now with the scores level.
Del Potro gets things underway in the third set, winning the first two points thanks to unforced errors from Djokovic.
Djokovic creates the chance to win a simple point but lashes a backhand into the net under no pressure. Very uncharacteristic from Novak and it costs him the opening game.
Del Potro can't make an impact on the Djokovic serve and we're quickly at 1-1 in the third set.
The Argentine tries a cross-court forehand which goes agonisingly wide. He challenges the call to no avail.
Big pressure for Del Potro on serve as another error puts him 0-40 down. Three break points for Djokovic.
Novak puts some wonderful disguise on a curling forehand and breaks to love early in the deciding set. All the momentum is now with the world number one in an incredible turnaround.
Del Potro has gone off the boil in the last 30 minutes after playing some superb tennis early on. He will have to find a break to stay alive in the tournament.
Djokovic is full of confidence and has got the forehand working after some early struggles. He quickly holds to love and is in complete control at 3-1 in the third set.
Del Porto gets back to basics on serve but can only produce a double fault to go 15-30 down.
Djokovic has a small opening taken away as Del Potro recovers to earn an imperative hold. He now trails 2-3 in the third set.
Djokovic continues to show his ruthless streak on serve. Keep this up and its hard to see a way back for Del Potro.
Del Potro tries to apply pressure but Djokovic creates a superb angle on his forehand and makes no mistake to hold comfortably.
The Argentine is back on serve and crunches the ball down the line for an easy ace. That serve is easily one of the most dangerous weapons in tennis today.
Djokovic is moving the big man around to brilliant effect here. He glides a drop shot in play effortlessly for a highlight reel winner.
Del Potro finds himself under pressure again but hangs on with a punishing serve at chest height to force deuce.
Break point to Djokovic as Del Potro lets a forehand drift wide.
Djokovic makes no mistake with an awesome forehand winner to claim a double break in the third set. Del Potro has run out of steam at the business end of this match and it's a real shame.
The world number one has produced when it matters and will now serve for the match.
Djokovic races into a 40-0 lead and its earns Three Match Points.
Del Potro crashes a forehand into the net and Djokovic wins the matc.h from a set down 4-6 6-3 6-2.
The tournament favourite struggled at times in the opening set but recovered brilliantly to stun Del Potro with an increased tempo in the later stages. He now advances to face either Andy Murray or Roger Federer in tomorrow's final.
Djokovic admits following a bruising encounter that securing a place in the final against Murray or Fed provided extra motivation. Tomorrow's final promises to be a classic.
Thanks for joining us at Sports Mole and be sure to check back in at 7.45pm tonight to see how Murray fares against Federer.
