SOME of the longest-running rivalries in world tennis may soon be consigned to the history books so it is heartening to note the arrival of another duel which seems destined to go the distance. Andy Murray taking on Kei Nishikori at tennis is a match-up which is made to happen, the kind of fixture which demands industrial quantities of popcorn to get you through. And that is just as a spectator. Think what it must be like as a participant.

From this year's stamina-sapping opener on Davis Cup duty back in Birmingham in February, taken by the Scot over five sets and five hours, to a grimly fascinating duel in the quarter finals at Flushing Meadows which went in the Japanese man's favour in just shy of four, there is usually only inches separating these two when they get it on. So it was yesterday as the World No 1 had to recover from the agonising loss of a first set tie-break to record the 6-7 (9) 6-4, 6-4 win which sees him rack up back-to-back opening wins at the ATP World Tour Finals for the first time.

Okay, so it wasn't quite the 11 hours which John Isner and Nicolas Mahut spent battering it out at Wimbledon one year, or the 4 hours 20 minutes of Roger Federer and Juan Martin del Potro's 2012 Olympic semi-final, but this was the longest three-set match in the history of these finals, only one minute shy of Murray's previous longest three set encounter.

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 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.

A respectable away support had made it into the o2 - I counted ten Japanese flags, maybe more - and they witnessed an assured start from their man, who like Murray had surrendered just five games when winning his ATP World Tour finals opener. While the Scot's return game gets him points on any opponent's serve, it was the Japanese man who was making the inroads early on. The World No 1 had a break point to save in two of his first three service games, the first saved by a service winner out wide then the second with a forehand down the line which was too much for Nishikori to handle.

After another break point each, here we were then, into a first-set tie-break which will live long in the memory, even if the sport seems to have served up more than its fair share of sensational deciders in recent times. It eventually went Nishikori's way, but not before the Scot had been forced to box clever on the ropes to keep himself alive. At one stage standing 6-3 down, Murray saved four set points, the most notable of which was the third, 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 16,000-strong Wednesday afternoon crowd went wild in recognition of the point of the tournament.

There was a more muted response 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 roars from the Scot signified the arrival of the first service break of the match, but it was perhaps inevitable that this match would enter something of a lull. Pegged back again at 4-4, a sweet running cross court backhand got the Scot's nose in front again and we were into the final set.

Now it was Murray who was making the inroads and when a Nishikori double fault gave him the double break for 5-1 some foolishly thought that was that. Nishikori forced him to serve for the match twice, but when a backhand flew long the No 1 remained on course for a sensational Sunday shootout with his other great rival, Novak Djokovic, to retain that ranking at year-end for the first time. Unless, that is, someone like Nishikori throws a spanner in the works.