( CNN ) -- Rafael Nadal sealed a remarkable comeback in 2013 by beating Stanislas Wawrinka at the ATP World Tour Finals on Wednesday to ensure he will finish the year as world No . 1 . The Spaniard also qualified for the semifinals of the only major tennis tournament he has never won , with the 27-year-old boasting a career grand slam in addition to an Olympic gold medal . Since returning to the sport in February after seven months out with a knee injury , the 13-time grand slam champion has won 10 titles in a year which he has described as one of his best . Beating Wawrinka in London confirmed that he finishes on top of the world for the third time in his career , with Novak Djokovic now forced to settle for second place . The Serbian had held the honor the past two years , while Nadal is the first player to win it back twice . `` A lot of emotions today , '' Nadal said following his 7-6 ( 7-5 ) 7-6 ( 8-6 ) over the Swiss eighth seed . `` It 's the perfect scenario to be finally the year-end No . 1 in this fantastic stadium , in front of this unbelievable crowd , so many thanks for making me feel like this . `` This has been an unbelievable comeback year . '' It certainly has . When he returned to action in Chile in February , Nadal moved so gingerly at times that he felt it better to leave some points as he attempted to protect his troublesome knee . A first title since the 2012 French Open followed later that month in Brazil , and these were soon followed by further triumphs in Mexico and Indian Wells . Comprehensive confirmation of the fact that `` the King of Clay '' had fully recovered his abilities came at the French Open when he beat Djokovic in a compelling semifinal before defeating compatriot David Ferrer to claim a record eighth title at Roland Garros . Humiliation followed at Wimbledon as the former champion was beaten by Belgium 's 135th-ranked Steve Darcis , the first time Nadal had exited a grand slam in the first round . Yet he recovered to clinch the U.S. Open in September , beating Djokovic in the final , and before a packed crowd at London 's O2 Arena on Wednesday , Nadal said his extraordinary return would have been impossible without his family . `` The team is everything for me , '' he explained . `` Without them , I would never have the chance to be back where I am today -- being the No . 1 at the end of the season when there are such unbelievable competitors in front of me . `` Without my family team behind me , it is impossible to think like this , especially after what happened last year . '' Swiss finals debutant Wawrinka now has a win and loss ahead of his final round-robin match against Ferrer , while Nadal will close against Tomas Berdych . Third-ranked Ferrer lost out to Czech Berdych in Wednesday 's late game 6-4 6-4 .
Rafael Nadal will be the year-end world No . 1 for the third time in his career . The Spaniard has won all four of his Grand Slam titles at Roland Garros and is unbeaten on clay since winning Wimbledon last year. Nadal also books place in semifinals of biggest competition he has yet to win .