Nikolay Davydenko wins the ATP World Tour Finals title in London . Serbian beats Juan Martin Del Potro of Argentina in straight sets . Davydenko was beaten in end of season final by Russian Bryan . Earlier , In the doubles final , American pair Bob and Mike Bryan Bryan brothers win doubles title to claim end of season top ranking .
Nikolay Davydenko wins the ATP World Tour Finals title in London . Serbian beats Juan Martin Del Potro of Argentina in straight sets . Davydenko was beaten in end of season final by Russian Bryan . Bryan brothers win doubles title to claim end of season top ranking .