Hello, and welcome to Sports Mole's live coverage of the encounter between Kei Nishikori and Andy Murray at the ATP World Tour Finals.

It's been a week since the final ball of the regular ATP Tour season was struck, but we have finally arrived at the start of the tournament that they've all been attempting to qualify for since the start of the year. Rafael Nadal is a notable absentee after appendix surgery, but with the likes of Djokovic, Federer and Murray in England's capital, the event has lost none of its glamour and prestige.

The world number one and defending champion Novak Djokovic gets underway tomorrow evening, but we are being treated to a fantastic opener to begin proceedings at the O2 Arena, which should be getting underway at around 2.10pm

Before we start to preview the upcoming match, I shall bring your attention to the tennis competition that we are currently running at Sports Mole. Up for grabs are £250's worth of tennis lessons that have kindly been made available by Wimbledon Debenture Holders. All the details can be found by clicking here.

So then, let's talk about Andy Murray, who is making his return to the 02 Arena after missing last year's event after undergoing back surgery. The two-time major winner had slowly but surely eased his way back onto the tour, while still putting together a number of last-eight and last-four appearances, but the last seven weeks have seen the 27-year-old discover some encouraging form on the way to picking up titles in Shenzhen, Vienna and Valencia. Murray lost his way a little against Djokovic at the Paris Masters but hopefully that was more down to fatigue than anything else.

As for Kei Nishikori, 2014 has been his breakthrough year. He was already established as a consistent top-20 but after a stunning run on the clay during the spring, that has provided him with the springboard to compete with the best players in the world. The confidence in his game came to the fore at Flushing Meadows in the summer when he beat Djokovic on the way to the US Open final and if he can produce similar displays today and throughout the week, he has every chance of going deep into the tournament.

The two players have emerged from their respective dressing rooms and are making their way towards a packed arena. No-one does it better than the O2 Arena when it comes to entrances in tennis.

As Murray walked onto court, there was a look in his eye suggesting how much he missed this tournament last year. It was also visible that plenty of nerves were present, but that's understandable for an occasion like this.

The Scot won the coin toss and chose to receive, maybe to give himself a chance to settle down into the match.

The head-to-head record between the two is in Andy Murray's favour. He's not even lost a set to the Japanese. I wouldn't really too much into that, though. It's been almost two years since their last meeting and Nishikori is a much improved player now than he was at the Australian Open in 2012.

The warm-ups are done and the two players are ready. It will be Nishikori, who is making his debut at this event, to serve first. Game on!

Murray starts with a couple of wayward backhands to give Nishikori the advantage before his opponent throws in a double fault. Nishikori comes out on top during the next point after a lengthy baseline exchange but a second double of the game keeps Murray in it. Nishikori takes the game though when Murray sends a backhand long.

Murray starts confidently enough, hitting a forehand winner before seeing a first serve return go long, which is followed by another return that doesn't make it into court. A love service game is completed when Nishikori nets. Good start on serve from the Scot.

After the first two points are shared, Murray dumps a return long to give Nishikori the lead before the Brit lashes a cross-court backhand marginally wide of the target. Nishikori comes close to a third double, but it proves irrelevant after a Murray drop shot gets the job done, before the home favourite digs deep at the net to get to deuce. The pair trade forehands from the baseline but Nishikori flinches first to give Murray a break point that is confidently saved. Murray is getting chances on Nishikori's second serve but as of yet, he can't capitalise and Nishikori holds.

Nishikori shows signs of settling down by outlasting Murray on the opening point, and the Japanese moves to 0-30 when Murray blasts a routine forehand long. The Scot is fortunate to get a second chance with a lob after Nishikori fails with a backhand smash before Murray registers the first ace of the match down the middle. Another meaty serve isn't dealt with by Nishikori and Murray completes the turnaround when a backhand down the line is netted by his opponent.

BREAK! Murray is gifted 0-30 when Nishikori hooks two groundstrokes into the tramlines, and that becomes 0-40 when Nishikori nets a backhand. Big chance here. The first opening is wasted when Murray goes long with a top-spin forehand before Nishikori saves the second with a smash. Can the US Open runner-up survive a third time? No, he can't! Another double fault from Nishikori gives Murray the first break of serve.

BREAK! It's Murray's turn to concede a double fault, and it's Murray's turn to fall 0-40 down after some super play from Nishikori. He's starting to go for his shots a lot more now. Wow, that's wild from Murray! A huge double fault concedes the break back to his opponent.

Nishikori is definitely putting more umph into his shots and it's allowing him to control the rallies. The Asian superstar gets to 30-15 but Murray shows his own power to level things up. An excellent return from Murray then brings up another break point but a backhand from Nishikori flicks the net to draw the error and he seals the game with a couple of blistering forehand winners from inside the court. Important game for Murray coming up now. He's second best at the moment.

After the opening two points are shared, Murray gets a confidence booster with a forehand winner and an ace to hold to 15. He needed that.

Murray gets a look at a second serve at 0-15 but he sends his return barely halfway up the net. He doesn't do anything off the next return either and Nishikori proceeds to wrong-foot the Scot with a backhand down the line. An ace gets Nishikori to 40-15 but excellent hand skills at the net from Murray keep him in the game. Another double fault from Nishikori, his fifth, takes the game to deuce but the Japanese constructs a shot-perfect point to help his seal the game.

SET! Nishikori looks hungry for the break here and an immaculate drop shot from the baseline gets him to 0-15. Murray's a tad fortunate to get to 15-15 after Nishikori slices long but once again, he outlasts Murray from the baseline to move two points away from the set. That becomes one as Nishikori runs around a second serve to nail the return down the line and it's two set points for the Japanese. Murray saves the first with a decent forehand but it's Nishikori's set when a backhand drop shot from Murray goes into the net.

Murray looked like he was in control when breaking for 3-2, but since then, it's almost been one-way traffic in Nishikori's favour. Murray's looked particularly tight on his second serve and that needs to improve in the second set.

Nishikori received treatment at the end of the set but he shows no ill-effects as he races to a love service hold. Murray needs a hold here or he could see this match run away from him.

BREAK! A big first serve gets him on the way, but Nishikori is all over a second serve again to level the score. There's a bit more intent from Murray, but his opponent is playing world-class stuff at the moment and a backhand winner makes it 30-30. Murray then goes long with a backhand and Nishikori has the chance to break, which he takes with a drop shot into the open court with Murray miles behind the baseline. It's a long way back from here.

Murray takes the first point after an error from Nishikori but he ruthlessly gets to 15-15 with a punishing forehand winner. A sixth double fault gives Murray a glimmer of an opening but two returns find the net to gift game point to the Japanese. A third miscued return from Murray is enough to concede a 3-0 deficit and he simply must hold when we return.

Murray looks in trouble at 0-15 but a crushing cross-court forehand finds the corner for 15-15. Can that liven him up? Not really. He takes the next point but a shocker of a second serve is given the treatment by Nishikori. The next rally sees Murray shows phenomenal reactions at the net but he then gets passed with an unreal backhand passing shot from Nishikori. Break point for Nishikori, but it's saved with an ace. Phew. Back comes Nishikori though, who is pummelling the ball from all angles, but he misses out on sealing the break by inches. Both players are producing some incredible tennis now to stay in the game and we get to a fourth deuce. Murray finally comes through with a forehand winner but that was an energy-sapping game for both men.

Nishikori gets to 30-0 in emphatic style, and that becomes 40-0 when Murray nets. However, a shot from Nishikori hits the net and goes out before a seventh double fault is recorded. Murray has hope, but Nishikori holds his nerve to convert a forehand winner.

A hold to love for Murray. It's been a while since we have been able to say that! He still needs to break Nishikori, though, and he hasn't come close on too many occasions since the fifth game of the match.

BREAK! Murray gets to 15-15 after Nishikori nets a forehand before the Scot makes things awkward at the net for his opponent to force the error before another mistake from Nishikori gives Murray two break points. He needs to strike here, and he does! Nishikori nets a volley and we are back on serve!

Murray's having some treatment to his left calf at the change of ends but it doesn't require a medical timeout.

Nishikori plays a terrific point to earn 15-15 and he should have 15-30 but some incredible defence from Murray as well as a poor forehand from Nishikori gets Murray to 30-15. The Scot then powers down an ace for two game points before sealing the game with another out wide.

Murray breaks a string when in a good position to move ahead and his new racquet isn't much better as he nets tamely. Nishikori records another double fault but it doesn't prevent him moving one game away from an impressive win.

MATCH! Nishikori was ruthless at this stage in the first set and he is adopting the same tactics here. He smashes his way to 0-15 before an immense backhand return finds the corner and Murray is in big bother. Nishikori miscues a return on the next point but the Japanese brings up two match points when Murray nets. He only needs one, though, and Murray goes long to give Nishikori an excellent win.

After fighting so hard to get back into the match, Andy Murray has lost his opening encounter at this year's ATP World Tour Finals. Murray was below par for much of the opening hour but he did well to come back from 3-0 down to get back to 4-4. However, he couldn't maintain his momentum and like in the first set, Nishikori struck when it mattered to get a win on the board.

On that note, we will end our coverage of this match but be sure to stay tuned for the remainder of the fixtures that will be played during the next eight days. Goodbye for now.