LONDON: Defending champion Novak Djokovic handed Nikolay Davydenko another defeat at the ATP World Tour Finals as the Serb secured a 3-6, 6-4, 7-5 victory on Monday.

Djokovic beat Davydenko to win the final of this prestigious end-of-year event 12 months ago and the world No 3, who also defeated the Russian in the group stage last year, came from behind to frustrate him again in his opening Group B match at London's O2 Arena.

Robin Soderling's surprise win over Rafael Nadal earlier had thrown the group wide open and Djokovic looks in the mood to mount a strong bid to retain the title. After reaching the final last year, Davydenko is in danger of being eliminated at the group stages this timeand will have to beat Nadal on Wednesday to keep his hopes alive.

Nadal is still some way short of his best after a traumatic, injury-hit season and Davydenko believes the Spaniard is struggling on the fast indoor court. "There is a difference between clay court and indoor. Sometimes it is pretty fast for him indoors," Davydenko said.