Djokovic wins Tour Finals by default as Federer bows out with back injury

World number one Novak Djokovic won the ATP World Tour Finals without even lifting his tennis racquet as 17-time Grand Slam champion Roger Federer withdrew from the final of the tournament because of a back injury.

The 33-year-old Swiss, who beat compatriot Stanislas Wawrinka 4-6, 7-5, 7-6 (8-6) on Saturday in a thrilling semifinal lasting two hours 48 minutes, announced he was not match-fit as he apologised in person to the crowd at the O2 Arena.

It is Djokovic's fourth victory at the season-ending event and he also becomes the first man to win three titles on the trot since Ivan Lendl in the 1980s, The BBC reported.

Federer, who has won the tournament six times, confirmed his withdrawal following the doubles final on Sunday afternoon, won by American brothers Bob and Mike Bryan.

He apologised to the crows for not being fit to play, and added that he hopes they understand. He said that he wanted to come out personally and explain.

The Swiss said that he did everything he could, took pain-killers, had rest until the very end, but added that he just cannot compete at this level with Djokovic. He claimed that at his age it would have been a risk.

Tournament organisers arranged two exhibition matches to take the place of the final, during which Djokovic defeated Britain number one Andy Murray 8-5 in a pro set in the first match and the British number one then paired up with John McEnroe to beat Tim Henman and Pat Cash 8-6 in a doubles contest.

Djokovic, who finished the year with only eight defeats from 66 matches, collected the ATP World Tour Finals trophy before his exhibition with the Briton.

The Serb admitted it's clearly not the way he wanted, adding that it's an incredible achievement, but at this moment it's hard to talk about it. He said that he is not one of the players that celebrate this particular type of win.

Federer is scheduled to join Switzerland team-mate Wawrinka for the Davis Cup final against France next week and said that his immediate plan was for recovery and then travelling to France and getting ready for the clay.