The 17-time Grand Slam champion said he hurt his back in the nearly three-hour semifinal win over Davis Cup teammate Stan Wawrinka on Saturday night in which Federer saved four match points.
"Unfortunately I'm not match fit,” the 33-year-old Swiss told the crowd at the
Fans appeared to be supportive with applause for Federer when he spoke.
Federer is set to play for Switzerland in the Davis Cup final against France, starting Friday. If he recovers in time, Federer will be chasing the only major trophy still eluding him. France hosts the match in the northern city of Lille.
Following back problems that ruined his 2013 season, Federer enjoyed a superb resurgence this season, losing to Djokovic in an epic
Federer, the most successful player at the ATP Finals with six wins, also made it to the semifinals at the
"I hurt my back late in the match yesterday against Stan, I am very disappointed and I hope to be feeling better soon," Federer added on his Facebook page. "It's been an extremely difficult decision because I love playing in London and the ATP World Tour Finals have been an absolute highlight of my career. Unfortunately, my back problem does not allow me to play right now."
Djokovic became the first player since Ivan Lendl from 1985-87 to win the year-end event three times in a row. He finished the season No. 1 for the third time in four years, becoming the seventh man to accomplish the feat at least three times. Besides winning his seventh Grand Slam title at the All England Club, Djokovic was also runner-up at the