Hello and welcome to LIVE game-by-game coverage of the final round robin matches in Group Stan Smith at the 2015 ATP World Tour finals. First up it's the already-qualified Roger Federer against Kei Nishikori. Later Novak Djokovic meets Tomas Berdych.

PERMUTATIONS FOR LATER: Berdych must defeat Novak Djokovic in straight sets to qualify. Federer would win the group with Berdych second. Any other result would see Fed-Ex topping the pool with Nole taking the runner-up berth.

GAME, SET AND MATCH! - FEDERER 7-5 4-6 6-4 NISHIKORI. Special K hits back from 15-30 down but double faults on game point to allow Fed a chance at deuce. It proves very costly as the Swiss snares match point before winning it with a thumping overhead. The six-time champion makes it three straight wins in the round robin to top the pool while Kei must now pack his bags for home.

FEDERER 7-5 4-6 5-4 NISHIKORI. Federer rediscovers his serving Mojo with his own hold to love in under a minute. A bit of pressure on Kei now. If he doesn't hold the match will be Fed-Ex's.

FEDERER 7-5 4-6 4-4 NISHIKORI. Kei pulls level once more! It's a classy hold to love with a sensational stun volley possible proof that this could yet be his day.

BREAK! - FEDERER 7-5 4-6 4-3 NISHIKORI. Kei's at it again! Is he about to pull off a sensational comeback from 4-1 down against Federer -TWICE!? A cracker of a game sees the momentum shift between the two players. An eighth ace looks to have put Fed in control but a glorious forehand winner on the run from Nishikori sees him snare break point. Roger saves it with lovely net play following up a piercing forehand and a big serve puts him back in control. But Kei won't give up and wrong-foots the Swiss with a delightful crosscourt drive from a tight angle before Fed offers up another break point with a double fault. This time the Japanese comes good and we are back on serve in the decider.

FEDERER 7-5 4-6 4-2 NISHIKORI. Fed treats his fans to the first sighting of the SABR at 40-15 down as hepummel the overhead away. Kei responds with a big serve and remains just the one break behind.

FEDERER 7-5 4-6 4-1 NISHIKORI. The Swiss holds to 30 and consolidates. He'll hope to see it out this time. It was 4-1 in the second set before he lost five games on the spin. Surely Kei can't turn it around once more?

Kei with the shot of the game, but one he ultimately lost. Will Roger see this out now... finally...?

BREAK! - FEDERER 7-5 4-6 3-1 NISHIKORI. Kei is made to pay for failing to make it count on triple break point as Fed shows him how to do it after a real battle of a game. Roger loses the point at 30-30 and lets fly with a rare profanity; a clear sign he's not happy with how things are going. The Swiss gives it everything on the next point and Nishikori helps him make deuce with an attempted winner down the line that snaps into the net cord. Kei is sent on another chasing around the court but comes up trumps with a delicious flat backhand winner down the line. Another scorcher is then called out and Federer ramps up the pressure, eventually doing enough to force his opponent to net following a tame second serve.

FEDERER 7-5 4-6 2-1 NISHIKORI. A strange decision to serve and volley on the second serve costs Fed as he trails 0-40. The Swiss looks ill at ease, apparently suffering with a cold, but he saves all three break points before Kei lashes an attempted winner just wide of the tramline on the right flank he is facing. The Japanese then contrives to thrash a poorly-timed forehand into the net to let Fed off the hook.

FEDERER 7-5 4-6 1-1 NISHIKORI. No problems for Kei as he clinches the hold to 15. He's worked so hard to get back in this, he'll be intent on ensuring he doesn't let it slip with a sloppy service game now.

Nice GIF of that Fed howler a bit earlier!

FEDERER 7-5 4-6 1-0 NISHIKORI. Federer shrugs off another awkward-looking shot that flies well wide at 40-15 by lashing down an ace to get off to a solid start in the decider.

Fed won just four of the last 22 points in that set as his 4-1 lead evaporated into a 4-6 loss.

SET! - FEDERER 7-5 4-6 NISHIKORI. We are going to a third-set decider! It's quite brilliant play from Nishikori with a wrong-footing winner to tee up two set points. Fed tries something different with a sliced drop shot but it slams into the net and he drops his first set of the week. Kei's hopes of qualifying for the last four are still alive!

BREAK! - FEDERER 7-5 4-5 NISHIKORI. What on earth is happening here?! Federer falls away badly at 30-15 and gifts Kei break point when comes into the net for a simple winner and pushes it way, way out of court. It results in screams of shock and horror from his fans. It's quite possibly a first of his career in terms of horrible misses and it's crucial as Kei snares the next point and will now serve for the set.