...match during the men's singles round robin match against Roger Federer of Switzerland during the Barclays ATP World Tour Finals at the O2 Arena on November 26, 2009 in London, England

...the ball through his legs against Roger Federer of Switzerland in a Singles match during the Barclays ATP World Tour Tennis Finals in London, on November 26, 2009

...Argentina gestures as he plays against Fernando Verdasco of Spain in a Singles match during the Barclays ATP World Tour Tennis Finals in London, on November 24, 2009

...during the men's singles second round match against Andy Murray of Great Britain during the Barclays ATP World Tour Finals at the O2 Arena on November 24, 2009 in London, England. (Photo by Julian...

Robin Soderling of Sweden plays against Rafael Nadal of Spain in a Singles match during the Barclays ATP World Tour Tennis Finals in London, on November 23, 2009

...reacts after the men's singles first round match against Robin Soderling of Sweden during the Barclays ATP World Tour Finals at the O2 Arena on November 23, 2009 in London, England. (Photo by Clive...

...ball during the men's singles first round match against Rafael Nadal of Spain during the Barclays ATP World Tour Finals at the O2 Arena on November 23, 2009 in London, England. (Photo by Julian...

Roger Federer of Switzerland plays against Fernando Verdasco of Spain in a Singles match during the Barclays ATP World Tour Tennis Finals in London, on November 22, 2009

...press conference at the Davidoff Swiss Indoors tennis tournament in Basel, Switzerland, Sunday, Nov. 1, 2009. The ATP tournament will last until Sunday, Nov. 8, 2009. (AP Photo/Keystone/Georgios Kefalas

Sweden's Robin Soderling returns the ball to Russia's Nikolay Davydenko during their ATP World Tour Finals tennis match at the O2 Arena in London, Friday, Nov. 27, 2009. (AP Photo...

Spain's Rafael Nadal reacts during his ATP World Tour Finals tennis match against Russia's Nikolay Davydenko at the O2 Arena in London, Wednesday...

Spain's Rafael Nadal changes his shirt during his ATP World Tour Finals tennis match against Russia's Nikolay Davydenko at the O2 Arena in London, Wednesday...

Spain's Rafael Nadal reacts during his ATP World Tour Finals tennis match against Russia's Nikolay Davydenko at the O2 Arena in London, Wednesday...

Sweden's Robin Soderling reacts during his ATP World Tour Finals tennis match against Russia's Nikolay Davydenko at the O2 Arena in London, Friday...

Novak Djokovic of Serbia celebrates on court after defeating Spain's Rafael Nadal in their ATP World Tour Finals tennis match at the O2 Arena in London, Friday, Nov. 27, 2009 . (AP Photo...