ANDY Murray admitted he was counting the days until the end of the tennis season after keeping his bid to be crowned Christmas No 1 on track with a gruelling 6-7 (9), 6-4, 6-4 win against Kei Nishikori which was the longest in the history of the ATP World Tour Finals. Despite saving four set points in an epic four-set tie-break, the Scot was extended the full distance by the No 5 seed from Japan. Having been victorious against him on Davis Cup duty over five hours in Birmingham back in February, then going down in just shy of four hours in the US Open quarter finals, this was just one minute shorter than his longest-ever three-set match, against Novak Djokovic at the 2012 Shanghai Open.

"We played five hours in Davis Cup, four-and-a-half at the US Open, three hours 20 minutes here, so we've played some quite long matches," said Andy. "I feel okay right now, it's the following day you feel stiff. I have hopefully got three matches left of my season. I'll do my best to get through as many matches as I can."

Nishikori, the No 5 seed here this week, has never won a Grand Slam, but that state of affairs won't last for long. The 26-year-old from Shimano, already blessed with with a massive following back home, is also possessed of a game with very few weaknesses. Without quite perhaps the Scot's instincts on the return nor his ability to punish himself in unlikely pursuit of balls which may never come back, he is an immaculate ball striker with great hands, a solid overhead and creativity around the net. He is also fast mastering the art of sneaking in there. Were it not for the red Uniqlo T-shirt and the sweatband at points it must almost have been as if Murray was playing against a mirror image out there.

The first-set tie-break here will live long in the memory, even if the sport seems to have served up some sensational deciders in recent times. It eventually went Nishikori's way, but not before the Scot had been forced to box clever on the rope to keep himself alive. At one stage standing 6-3 down, Murray saved a total of five set points, the most notable of which was the third one, when sheer instinct alone saw him converge onto a Nishikori volley after for once he had half-hit a lob. He somehow steered the ball into the court and the crowd went wild in recognition of perhaps the point of the tournament.

There was a different response from the 16,000 souls crammed in here on a Wednesday afternoon in London when the breaker eventually went the way of Nishikori by an 11-9 scoreline, courtesy of a ground stroke which landed flush on the baseline, but the World No 1's mental fortitude as much as his physical strength has taken him thus far and he wasn't about to panic now.

One of those trademark Murray roars signified the arrival of the first service break of the match, and while Nishikori pegged him back again at 4-4, a sweet running cross court backhand got the Scot's nose in front again and before we knew it we were into the final set.

Now it was Murray who was making the inroads and when a double fault from the Japanese man gave him the double break for 4-1 some mistakenly thought that was that. The Japanese man made him serve for the match twice, and when a backhand flew long the No 1 remained on course for a sensational Sunday shootout with his other great rival, Novak Djokovic. Unless, that is, someone like Nishikori throws a spanner in the works.

"He was making me run a lot, but I was starting to get some free points on his serve," said Murray afterwards. "I managed to get enough points to win. That's what you work for, in the big moments in big matches, and in an amazing atmosphere. That's why you put the work in."