Novak Djokovic came from a set down to defeat Nikolay Davydenko in his opening match in the ATP World Tour Finals.

Djokovic - who defeated Davydenko in last year's final in Shanghai - lost his serve twice in the opening set, before battling back to overcome the hard-working Russian 3-6 6-4 7-5.

Both players started the match solidly and held their opening two service games before Davydenko struck in the fifth game.

His flat groundstrokes brought up three break points and the break was confirmed when Djokovic netted a backhand.

The Serbian had his chance to break back in the next game, but Davydenko dug in to hold serve for a 4-2 lead after Djokovic went long.

Both players then held serve to leave Djokovic serving to stay in the opening set.

However, his Russian opponent took the initiative and some good play at the net brought him two set points, and he converted the first with a precise lob to win the first set 6-3.

Davydenko held serve at the start of the second, and Djokovic responded to level the score, before the frustration of losing the first set was there for all to see as he came close to breaking Davydenko's serve but the Russian held on, which resulted in Djokovic smashing his racket to the amusement of the O2 crowd.

After holding serve, Djokovic again came close to breaking serve after earning himself two break points but Davydenko held firm once again to remain ahead at 3-2.

The match continued on serve until 4-4 when Djokovic finally got the breakthrough his play had deserved. His Russian opponent netted twice and went wide with a forehand on break point to give Djokovic to serve to take the match to a deciding set.

Despite requiring to save a break-back point, he duly delivered on his first set point to ensure this entertaining match goes the distance.

Djokovic had gained all the momentum in the match and he continued that dominance with another break at the start of the third set after capitalising on a fortunate net cord.

He held comfortably for his fifth consecutive game before Davydenko stopped the rot with a service hold.

Both players held serve before Davydenko earned two break-back points in the sixth game of the set. They came and went and he missed out on a further break point after netting a forehand.

Three consecutive service games without incident saw Djokovic lead 5-4 and needing to serve out to win the match, but Davydenko had other ideas.

He took advantage of a couple of nervy points from Djokovic before firing down an awesome backhand down the line to level up at 5-5.

However, after delivering arguably the shot of the match, the Russian faltered under the pressure on his serve and was easily broken to love to hand Djokovic a second chance to serve for the match.

This time, he made no mistake as he opened up a 40-15 for two match points, and despite Davydenko saving the first with a forehand winner, he went long on the second to give Djokovic an hard-earned victory.
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