Nikolay Davydenko [ Images ] beat weary Argentine Juan Martin del Potro [ Images ] 6-3, 6-4 to claim the ATP World Tour Finals title at the O2 Arena on Sunday.

The wiry Russian, who has climbed to sixth in the world this week, produced a faultless display to claim the biggest title of his career and a $1.5 million cheque.

Davydenko, 28, broke Del Potro's serve in the fourth game and then pounced again at 4-4 in the second set before serving out for victory in one hour 23 minutes.

"For me it was amazing to come here ranked at seven and to win the tournament, I surprised myself," Davydenko said on court in front of another 17,500 sell-out crowd.

Davydenko's challenge began with defeat last Monday against Novak Djokovic [ Images ] in his opening round-robin match but he recovered with inspired victories over Rafael Nadal [ Images ], Roger Federer [ Images ] and finally Del Potro, players who between them won all the grand slam prizes on offer this year.

Del Potro, the US Open [ Images ] champion, looked flat throughout the contest and never really got a foothold in the match that Davydenko dictated from start to finish.

Only once did he threaten to make a real match of it, when he created chances to break the Davydenko serve midway through the second set.