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 27 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.