LEAD: Djokovic in danger after London loss to Tipsarevic

By Bill Scott Nov 25, 2011, 17:01 GMT

London - The superb season of one-time tennis dominator Novak Djokovic went well off the boil on Friday as the world number one was defeated 3-6, 6-3, 6-3 in a final group match at the ATP World Tour Finals by substitute Janko Tipsarevic.

Djokovic, who started the month with just two losses and 10 titles in 2011, has now suffered his fourth defeat in less than three weeks.

His fate at the year-end event now hangs in the balance, with one scenario in the final group match leading to elimination for the Serb.

The other group has been set, with undefeated Roger Federer and Frenchman Jo-Wilfried Tsonga booking the Saturday semi-final places.

The disappointed Djokovic can only now watch his destiny at event unfold.

Should Spain's David Ferrer (already qualified) beat Czech Tomas Berdych in the closing group match, Djokovic will go through as second in the group. A Berdych win would eliminate Djokovic.

The match with Tipsarevic was a disappointment for Djokovic, who had beaten his good friend and frequent practise partner - who came on in place of injured Andy Murray this week - in all three of their previous matches.

This time, Djokovic went down in a flurry of errors, with his serve broken four times in just over two hours.

Djokovic, still a highly respectable 70-6 on the season of his life, looked scratchy in the opening set but won the first set after Tipsarevic saved a pair of set points in the penultimate game of the opener.

Djokokvic, who ended 1-2 in group play, was unable to close out a win in a second set which featured three consecutive breaks of serve. Ninth-ranked Tipsarevic profited for 5-3 after his opponent double-faulted to yield a break point, with Djokovic then returning long.

Tipsarevic levelled the match a game later at a set each. Momentum picked up for Tipsarevic in the third set, with the challenger breaking in the opening game and holding the margin to clinch the win on the second of three match points.

Djokovic, the first ATP player to win at least 10 titles since Federer's dozen in 2006, was trying to reach his 14th semi-final in 15 tournaments this season.

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