( 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 . Spaniard beats Switzerland 's Stanislas Wawrinka at ATP World Tour Finals in London . Nadal also books place in semifinals of biggest competition he has yet to win .