LONDON — Rafael Nadal guaranteed he will finish 2013 on top of the world rankings with a 7-6 (7-5), 7-6 (8-6) victory over Stanislas Wawrinka at the ATP World Tour Finals Wednesday. Nadal arrived for the prestigious season-ending event knowing two Group A victories at London's O2 Arena would be enough to ensure he couldn't be caught by second placed Novak Djokovic in the race for the No. 1 ranking. The Spaniard achieved that aim in typically dominant fashion, beating Swiss seventh seed Wawrinka 24 hours after opening the tournament with a straight sets win over David Ferrer. It is the third time Nadal has finished a calendar year in pole position in the rankings — and the first since 2010 — and he celebrated with a jubilant jig around the court. He is the first player to end a year at No. 1 three years after his last season-ending top spot. The 27-year-old's straight sets victory over Wawrinka also booked his place in the semifinals of the Tour Finals, with one group match against Tomas Berdych still to come. Nadal has insisted he isn't overly concerned about rankings these days, but his return to the top is a remarkable achievement given he only came back in February after seven months out with severe knee tendinitis that threatened to cut short his career. Since his return from injury, Nadal has won the French and US Open titles, as well as eight other tournaments, and a maiden triumph at the Tour Finals would be a fitting end to such a memorable campaign. Wawrinka has enjoyed the best season of his life, qualifying for the Tour Finals for the first time and winning his career-best 50th match of the year with a three-set victory over world No. 5 Tomas Berdych Monday. Novak Djokovic got the better of Roger Federer for the second time in three days as the Serb started the defense of his title with a 6-4, 6-7 (2-7), 6-2 win Tuesday. Just 72 hours after their last meeting ended in a victory for Djokovic in the semifinals of the Paris Masters, the two old rivals were back in conflict across the English Channel and they produced another gripping Group B encounter at London's O2 Arena. Once again Djokovic had the upper hand as the world No. 2 began his bid for a third crown at the season-ending tournament by repeating his victory over Swiss great Federer in last year's final. Neither player was at his best, with Federer making 45 unforced errors and Djokovic 33, but the erratic quality of the tennis couldn't detract from the drama. Since losing the US Open final to Rafael Nadal in September, Djokovic has played like a man on a mission to erase the bitter aftertaste of that defeat. This was his 18th consecutive victory since trudging off court as a loser in New York, a run that has brought him titles in Beijing, Shanghai and Paris, and another crown in London looks a distinct possibility. In contrast, after one of the worst campaigns of his illustrious career, Federer has tumbled to sixth in the world rankings and will fail to finish the year as a member of the world's top four for the first time since 2002. In the doubles match Wednesday Spaniards David Marrero and Fernando Verdasco beat Leander Paes of India and Radek Stepanek of the Czech Republic 6-4, 7-6 (5). — Agencies
