So that is everything from the first semi-final. We will be back at 20:00 GMT, for the second semi-final between Roger Federer and Stan Wawrinka. We will see you then. Bye for now.

Andrew Castle
BBC tennis commentator on BBC Two

Image source, Reuters

Nishikori will end the year as world number five, having started it as number 17, aided by that appearance in the US Open final. It's been a sensational year for him.

Some words from our winner Novak Djokovic: "Kei was playing great and this has been the best season of his life but he made some crucial double faults in the third set.

"Of course I will watch the semi-final [between Roger Federer and Stan Wawrinka]. I'll get some popcorn and enjoy it from my bed."

Novak Djokovic may be a bit more tired than he would like. He tries to sign the television camera with a bright yellow pen, but instead just leaves a dot on the screen, before he gives up.

But, he has certainly made his mark on the tournament.

He will face the winner of the second semi-final between Roger Federer and Stan Wawrinka on Sunday.

Andrew Castle
BBC tennis commentator on BBC Two

"What a sad way for it to end but it's Djokovic who secures his place in the final where he will try to make it three in a row."

He needs something special now, does Nishikori. But he loses the opening two points off his own serve. A cross-court winner after a Djokovic volley brings a smile to his face to make it 30-30, but an even better cross-court forehand from Djokovic gives the Serbian his first match point.

It is all over. A double fault. ends it.

Image source, AFP

Tim Henman
Former British number one on BBC Two

"It will be a big disappointment if Nishikori's last set of the year is a bagel. I'd like to see him hold serve here."

Image source, AFP

The head is down, the shoulders are slumped. There looks no way back for Nishikori. He is galloping around frantically, but it is not enough. The class of Djokovic has proved decisive. He needs one more game. Nishikori serving to stay in the match.

Tim Henman
Former British number one on BBC Two

"He battled so well in the second set to stay in it but here he is 15 minutes later and 4-0 and two breaks down in the decider."

Nishikori certainly has not given up, but is struggling for consistency. A double fault, his second of the set, puts him under more pressure, although he responds with an ace. His next point? Another double fault.

Those two mistakes help Djokovic move to break point, which he takes full advantage of. Nishikori throws his racquet to the floor in frustration. The racquet has gone. The match may soon be gone as well.

Good sportsmanship from Djokovic in the third game. A spectacular backhand cross-court winner from Nishikori is applauded by Djokovic. He was unimpressed with the crowd cheering on his opponent earlier in the match, but that was nice to see.

But that backhand winner can not lead to a break. Djokovic is back on top and looks just too good. He is now 3-0 ahead. Surely a place in the final is going to be his now?

Andrew Castle
BBC tennis commentator on BBC Two

"Djokovic's indoor streak stands at 30. Ivan Lendl once won 37 on the trot, while John McEnroe holds the record at 59."

Image source, AFP

Break point for Djokovic now after Nishikori gives it too much welly and sees a forehand go long. Another one is overhit, which could give Djokovic the break.

It is challenged by the Japanese, but the umpire's call was correct. The ball was out. Djokovic back in charge.

Piers Newbery
BBC Sport at the O2 Arena in London

"Finally this week, some real, big match drama. Djokovic barely made a winner after being annoyed by the crowd and he might well have been even more upset had Nishikori taken one of those two break points at the start of the decider.

"The Japanese player is, somewhat surprisingly, statistically the most successful player in the open era in deciding sets, and leads the ATP this year with a 21-2 record. A real test for the world number one who has won 14 of 16."

Tim Henman
Former British number one on BBC Two

"It was a great opportunity for Nishikori in that first service game. But now the momentum changes."

The first set only took 23 minutes and it looked routine for the world number one, but Djokovic is having to battle hard for every point.

Nishikori, off Djokovic's serve, takes the opening two points, but is then furious with himself when he drags an angled forehand out.

However, an off-balance Djokovic then throws one well off target and Nishikori has two break points. The first ends disappointingly for him, with the ball in the net. The second one follows suit, and we're back at deuce.

Djokovic does the rest. The final point sees Nishikori diving the wrong way, like a baffled goalkeeper who has been given the eyes by a skilful penalty taker.

Some stats for you from the second set...

Set time: 37 minutes

Winners: Nishikori 10, Djokovic 3

Unforced errors: Nishikori 5, Djokovic 8.

The world number one has lost a set for the first time this week. How will he respond?

Tim Henman
Former British number one on BBC Two

"Djokovic's concentration levels dropped off after he was broken for the first time. It's going to be important mentally how both players come out at the start of the second set. I'm expecting a big reaction from Djokovic."

It is a great time to produce your first ace of the match. Nishikori then has two set points. He only needs one of them. Djokovic's return goes wide to the left of the court and Nishikori takes the set. This match looked all over half an hour ago. Now it is one set each.

Tim Henman
Former British number one on BBC Two

"He's been crushing his forehand well and suddenly from a set and a break down, Nishikori is serving for the second set."