LONDON (AP) -- Defending champion Novak Djokovic defeated six-time winner Roger Federer 6-4, 6-7 (2), 6-2 at the ATP World Tour Finals on Tuesday, improving his chances of overtaking Rafael Nadal in the race for the year-end No. 1 spot.
Playing his first round-robin match at the elite tournament this year, Djokovic extended his winning streak to 18 matches after capturing his sixth title of the season last week in Paris. He beat Federer in Paris in the semifinals.
Djokovic is trying to finish No. 1 for the third year in a row. Nadal, who eased past David Ferrer 6-3, 6-2 earlier Tuesday, needs only one more win in London to be guaranteed of the top spot.