London:Novak Djokovic kept alive his chances of reaching the semifinals of the ATP World Tour Finals by beating Rafael Nadal 7-6 (5), 6-3 on Friday and handing the Spaniard his third straight loss in the tournament.
It was the third-ranked Serb's second win of the round-robin phase, but he still needs Robin Soderling to beat Nikolay Davydenko in the late Group B match to advance. Soderling has already advanced.
Nadal struggled for the third match in a row and finished with nearly three times as many unforced errors as winners _ 35 to 12. He needed medical treatment on his lower back at 2-1 in the second set, and was broken in the next game.
The second-ranked Spaniard saved two match points in the final game before sending a backhand wide on the third.
Djokovic had even more errors _ 37 _ but hit 21 winners and made fewer mistakes than Nadal when it mattered.
Nadal had broken back twice in the first set to reach the tiebreaker, where he shanked a couple of forehands and quickly fell behind 6-2. He saved three set points before sending a forehand wide on the fourth.
The Spaniard showed flashes of his speed, chasing down a number of Djokovic's drop shots at the net. But his efforts were usually in vain, as most of his returns merely resulted in easy volley winners for the Serb.
Nadal leaves the tournament without having won a single set, and is now on a four-match losing streak after losing to Djokovic in the semifinals of the Paris Masters this month.
The Spaniard, whose season has been interrupted by injuries, is just 1-9 against top-10 opponents since losing to top-ranked Roger Federer in the Madrid Masters final in May.
If Djokovic advances, he can overtake Nadal for the No. 2 ranking by winning the tournament.
In the other group, Federer and Juan Martin del Potro reached the semifinals Thursday, while Andy Murray was eliminated. Fernando Verdasco of Spain, Nadal's teammate in next weekend's Davis Cup final against the Czech Republic, also went 0-3 in the round-robin phase.