Novak Djokovic
Djokovic prevailed in two sets against Nadal.

Novak Djokovic claimed a 22nd consecutive win to remain the ATP World Tour Finals champion after dismissing world No.1 Rafael Nadal in straight sets at London's O2 Arena.

Djokovic retained his crown from 2012 by winning 6-3 6-4 in an anticlimactic end to the season as Nadal's gallant return from injury finally caught up with him.

The tour finals crown remains the only major title missing from Nadal's CV but after a year during which he rose to the summit of the ATP rankings and won two grand slam titles following seven months out with a knee injury, he remains among the primary narratives of the season.

But the final significant contribution of the year came from Djokovic, who is the unbeaten champion in Greenwich on a second successive occasion, prior to spearheading Serbia's assault on the Davis Cup against Czech Republic next week.

The end to the 2013 had seemingly been handed the fitting finale as the world's top two players squared off in London for a 39th time with Nadal chasing an elusive first world tour title after confirming that he will finish the year as world No.1, while Djokovic was protecting a 21-match unbeaten run since the US Open.

The week had begun with both players suggesting that the tour finals be moved away from London, the home of the season ending event since 2009, but neither had shown the desire to make their stay in the English capital at all brief, each reeling off four successive wins in unmistakable style this week.

Those same heroics would accompany the opening set of their latest titanic tussle. Djokovic first hit the front, pinning Nadal back with an accurate forehand chip to which the No.1 seed was unable to mount a reply, to surge into a 3-0 lead.

The Serbian could have had one hand on the first set had he capitalised on two Nadal double faults in the fourth game but a superbly placed backhand nullified Djokovic and secured the hold.

And the save inspired a break-back from Nadal as Djokovic made two errors on the backhand side, finding the tramlines with a pair of cross-court passes before Nadal struck in his third break chance of the game.

Two further double faults from Nadal against pilled the pressure on but this time the French and US Open champion was unable to respond. Following an engrossing point, Djokovic produced a herculean effort to keep out a backhand before he prevailed in a lightning net exchange to break again.

Djokovic did serve out the first set, but not without alarm as Nadal produced a brilliant overhead backhand volley to create a break-back chance, but the Australian Open champion snuffed out the opportunity to lead by a set.

The depth to the Djokovic return was becoming an increasing problem for Nadal and the six-time major winner quickly had a second set break to reflect his dominance in the rallies, after a stinging backhand service return.

Nadal was unable to muster anything from a imperious Djokovic serve and had to save a championship point serving at 5-4 down in order to force his opponent to serve out the match.

Not knowing when to lie down, Nadal saved a second championship point with a cross-court drop but Djokovic eventually prevailed at the third time of asking to spark scenes of wild celebration.