Hello, and welcome to Sports Mole's live coverage of the last-four contest between Novak Djokovic and Kei Nishikori at the ATP World Tour Finals.

After six days of intense group-stage competition, we have finally arrived at the semi-final stage of the ATP World Tour Finals, and, taking into consideration Rafael Nadal's absence, it's fitting that the top four players of 2014 have made the latter stages in London.

Despite the first doubles semi-final only finishing around 15 minutes ago, we look set to get underway on time. Nishikori enters the area to a polite reception but the decibel level goes up a notch upon the arrival of the world number one.

Talking of Djokovic being world number one, that position was sewn up for the remainder of the year after he eased past Tomas Berdych yesterday afternoon. It was another stunning performance from Djokovic, who has put together an almost untouchable record indoors in recent times. He's won his last 27 sets in these conditions!

While much of the focus regarding Djokovic is whether he can defend his title in London, the main focus on Nishikori is whether he will be hindered by an ongoing wrist niggle today. He insists that it won't be a factor, and it hasn't been during wins over Andy Murray and David Ferrer, but it's something that has required attention throughout the tournament. Fingers crossed it won't stop him giving Djokovic a match over the next couple of hours.

Back in Paris a couple of weeks ago, Djokovic thrashed Nishikori but the Japanese superstar will take confidence from his previous performance against the Serbian when he won in four sets at the semi-final stage of the US Open. It's a much slower surface in London, but Nishikori does possess the firepower to cause a surprise today.

The warm-up has flown by and we are ready to get underway. It will be Djokovic to serve first.

Djokovic takes two of the three opening points with imposing one-twos behind his first serve before rushing Nishikori after ghosting into the net for two game points. The game is sealed with another Nishikori mistake and that's the kind of start that he would have been hoping for.

Nishikori needs to make a strong start on serve and it's looking promising when he curls one out wide for 15-0, but Djokovic is keen to take the Japanese's belief away early and he fights for a 15-30 advantage. Nishikori responds to get to game point, despite some outrageous defence from Djokovic, and a heavy serve out wide gets the US Open runner-up on the board.

An ace out wide and a first serve down the middle see Djokovic race to 30-0 before Nishikori sends a backhand return inches long of the baseline. A second ace of the game seals a love hold for Djokovic and he's soon into his groove here.

BREAK! Djokovic gets lucky with a net cord to smash a forehand winner past Nishikori for the opening point and when Nishikori can't get any elevation on a cross-court forehand, the danger signs are there for the 24-year-old. Djokovic misses out with a forehand on the next point, but he has two break points when Nishikori floats a backhand long of the baseline. A well-executed serve out wide saves the first but it's disaster for Nishikori at 30-40. He constructs a superb point but misses out with a backhand volley at the net. First blow to the world number one.

This is as good as Djokovic has served all week. An ace and two unreturned serves see him get to 40-0 with little fuss before a one-two which concludes with a thunderous forehand winner into the corner seals a second love hold in a row.

BREAK! At 0-30 down, Nishikori is in danger of falling a double-break down but Djokovic misses out twice, both by small margins, to allow him to get to 30-30. A double fault from the Japanese concedes break point but some aggressive play from the baseline earns deuce. It's a momentarily blip for Djokovic, though, who powers his way to 5-1 with more relentless hitting from both wings.

SET! More dominant serving takes Djokovic to three set points, but newsflash - he is human! The world number one misses the easiest of volleys to concede just his second point on serve in four service games, but he seals the set on the next point. That lasted 23 minutes.

Nishikori won just 11 points in that first set. The level of Djokovic's play has been unreal.

BREAK! The Japanese opens with a double fault but he responds with a blistering forehand winner that suggests he may just try to hit his way through his opponent. That's doesn't looking like working though, and two Nishikori errors hand more break points to Djokovic. He saves the first with some aggressive play but another forehand error gifts the Serbian the break.

BREAK! The crowd are desperately trying to rouse Nishikori. They want to see a longer match. He takes the opening point before nailing a second-serve return to stay competitive at 30-30. Djokovic then dumps a forehand into the net and it's break point to Nishikori! This is huge. DOUBLE FAULT! Nishikori breaks and Djokovic looks rattled. He's just sarcastically applauded the crowd, believing that they contributed to that. Very harsh.

Have the tables turned? Nishikori holds to 15 with minimal fuss and for the first time in the match, Djokovic has some work to do.

Djokovic has composed himself but there's certainly a bit of frustration lingering. He lashes a forehand into the corner for 30-0 before a couple of first serves are enough for a love hold - his third of the match.

Nishikori looks in command at 30-0 but a drop shot is easily picked off by Djokovic. The world number one looks on course for 30-30 but Nishikori survives with a forehand winner, much to the delight of the crowd. The hold is sealed when Djokovic sends a return long.

I tell you what, Nishikori is warming to this. He crunches a cross-court forehand winner for 0-15 but how unlucky can you get? A Djokovic slice clips the top of the net and drops agonisingly over Nishikori's side of the net. The pair trade winners off the ground before a Djokovic first serve hands him the initiative to hold for 3-3.

More often than not, Nishikori is trading with Djokovic from the back of the court with better effect and it helps him get to 40-15. He slices a backhand long but after forcing a mistake for Djokovic off the same wing, he ensures that the set remains on serve and if that continues from here onwards, the pressure is going to build on Djokovic.

It's also worth noting that Djokovic has conceded five games in a match for the first time this week. This looks concerning though. Nishikori is having some treatment to his wrist.

BREAK! A double fault from Djokovic gives Nishikori the perfect start before a cross-court backhand from the Japanese earns him 15-30. A huge first serve gets Djokovic back on level terms but it's BREAK POINT TO NISHIKORI when he smashes a forehand winner into the corner. Can Nishikori strike? HE CAN! Incredible, incredible tennis. One of the exchanges of the week see Nishikori draw Djokovic in before converting a forehand passing shot. He is serving for the set!

SET! At 15-15, Djokovic challenges an ace from Nishikori but he's wrong! It's 30-15 to Nishikori and that quickly becomes two set points when Djokovic nets. A swinging serve out wide from Nishikori is enough to take the set and from a break down, somehow, some way, Nishikori has made it a set apiece.

Nishikori has won five out of the last seven games. He's playing at the top of his game right now, but Djokovic's level has dropped enough to give the Japanese the openings that he wasn't previously getting.

All of a sudden, this is an important game for Djokovic, but he's in huge trouble when finding himself 0-30 down. He's lucky to survive the next rally but Nishikori has two break points when Djokovic hooks a forehand wide. They are both squandered though with two shots into the net. How crucial will that be? Djokovic holds.

BREAK! At 15-15, Nishikori could do with a couple of first serves but a double fault gives Djokovic the momentum. Nishikori hits his way to 30-30 but the same tactic doesn't pay off twice in succession and it's break point for the world number one. The pair become embroiled in a rally but Nishikori goes long to fall behind.

Nishikori loves the cross-court drop shot but Djokovic has become wise to it and executes one of his own for the opening point. Back comes Nishikori with a thumping backhand winner but like in the previous game, the same trick doesn't pay off twice. Nishikori survives a game point with a forehand put-away but Djokovic has regained his accuracy on serve and it's enough for the hold.

BREAK! This is simply a must hold for Nishikori and he starts positively for a 30-0 advantage but Djokovic stops him racing away with the game by crushing a backhand down the line. The Japanese then throws in double faults either side of an ace to give Djokovic deuce and that soon becomes double-break point when a net cord allows Djokovic to step in and convert a forehand. It's taken when Nishikori tamely nets, and that, folks, could be that.

Djokovic is going through the motions now. Two first-serve returns miss the target before he puts away a smash. A love hold is sealed with a strong delivery out wide to move just one game away from the final.

MATCH! Nishikori is still trying to fight against inevitable defeat but he can't withstand Djokovic's power during the opening two points and he's on the brink. However, he storms back with two forehand winners from inside the court but Djokovic powers a cross-court forehand winner for match point. That was superb. It's quite fitting that it ends this way - Nishikori has had trouble with them all tournament - but another double fault has put paid to his time in London and Djokovic is through to another final at the ATP World Tour Finals.

It was more competitive than it looked like being at one stage but Novak Djokovic is through to tomorrow's final. He endured a blip in the second set but for large parts of this contest, Djokovic was at his best and it's going to take some effort from either Roger Federer or Stanislas Wawrinka to stop the world number one from defending his title.

That will be all from Sports Mole's coverage of this match but we will be back at 8pm for the all-Swiss showdown between Federer and Wawrinka. Goodbye for now.