Serbia's Novak Djokovic celebrates winning his ATP World Tour Finals tennis match against Russia's Nikolay Davydenko at the O2 Arena in London, Monday Nov. 23, 2009. AP Photo logo AP Photo 3 months ago

Serbia's Novak Djokovic celebrates winning his ATP World Tour Finals tennis match against Russia's Nikolay Davydenko at the O2 Arena in London, Monday Nov. 23, 2009.