Roger Federer wanted to end the year with a bang, but the Swiss tennis superstar had to pull out of his finals showdown with Novak Djokovic at the 2014 ATP World Tour Final on Sunday.

Federer addressed the crowd one hour before the match, saying that he cannot play against Djokovic in the final, citing a back injury that he sustained during his three-hour semis match against compatriot Stan Wawrinka on Saturday, where he had to save four match points.

"Unfortunately I'm not match fit," Federer told the crowd at the O2 Arena in London. "I tried everything I could last night, also today: painkillers, treatment, rest, so forth, warm-up, until the very end. But I just can't compete at this level with Novak. It would be too risky at my age to do this right now and I hope you understand."

The 33-year-old tennis superstar, who was aiming to win his seventh ATP World Tour Final title, withdrew from a match just for the third time in his career. He was also forced to withdraw due to a back injury in 2008 Paris Masters and in Doha in 2012.

"I think you have some recurrent things coming back from time to time," Federer said. "It's not that much of a surprise. I must say I've been feeling really good for over a year now, which has been not a surprise, but it's been very nice. So this back spasm, whatever it might be, it's just not a fun thing to have during the day."

Following his decision to withdraw, some fans wondered if Federer's decision had something to do with his upcoming stint in the 2014 Davis Cup final where he will look to lead Switzerland to a win against France.

Novak Djokovic said, though, that he does not think Federer decided to withdraw because of the Davis Cup, saying that the former World No. 1 told that he will also be doubtful for Switzerland.

"I don't think he was calculating and trying to save his body for Davis Cup final," Djokovic said. "This is probably the biggest match of the season next to the final of a Grand Slam. I spoke to him, it's a question mark for the Davis Cup final as well."