LONDON, Nov 27 (Reuters) - Rafael Nadal's misery was complete on Friday when he lost 7-6 6-3 to Novak Djokovic at the ATP World Tour Finals meaning he will pack his bags for Spain having failed to win a solitary set in his three matches.

Djokovic kept alive his hopes of reaching the semi-finals but he will have to wait until Nikolay Davydenko takes on already qualified Swede Robin Soderling in the final round-robin match of the season-ending event at the O2 Arena before knowing if his two Group B victories will be enough.

Davydenko would squeeze out Serbia's Djokovic should he beat Soderling by virtue of a better sets win/loss ratio.

Nadal, who could lose the world number two spot if Djokovic goes on to win the tournament, once again looked a shadow of the player that began the year in such devastating fashion by claiming the Australian Open title.

"It's not very disappointing, no," Nadal told reporters before packing his bags for Spain where he will prepare for next weekend's David Cup final against the Czech Republic.

"It's only disappointing if you arrive here with the feeling that you have a big chance to win. But I didn't arrive here with that feeling."

He lost his opening two services games although his instinctive battling qualities allowed him to break Djokovic twice to stretch the opening set into a tiebreak.

Some weak baseline errors allowed Djokovic to forge into a 6-2 lead before Nadal won the next three points only to loop a harmless looking forehand into the tramlines, one of 35 unforced errors that littered his game.

Nadal needed treatment on his lower back at 1-2 in the second set. He dropped his serve again in the following game with yet another forehand error and Djokovic stayed out in front to claim victory in one hour 57 minutes.

In Group A, which concluded on Thursday in confusing circumstances when three players ended with almost identical records, world number one Roger Federer and Juan Martin del Potro moved through to the semi-finals.

(Editing by Alison Wildey; to query or comment on this story email sportsfeedback@thomsonreuters.com)

((martyn.herman@thomsonreuters.com; +44 20 7542 7933; Reuters Messaging:martyn.herman.reuters.com@reuters.net. For the new Reuters sports blog Left Field go to: http://blogs.reuters.com/sport/))

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