LONDON -- Novak Djokovic remains the man to beat on indoor courts. The defending champion made quick work of top-ranked Rafael Nadal 6-3, 6-4 to win the ATP World Tour Finals on Monday, extending his winning streak to 22 matches and claiming the elite season-ending title for the third time. Djokovic, who has not lost a match since his defeat to Nadal in the U.S.