Switzerland's Roger Federer serves to Jo-Wilfried Tsonga of France during their round robin singles match at the?ATP World Tour Finals on Sunday, Nov. 20, 2011.

Five-time champion Roger Federer began his title defence at the ATP World Tour Finals on Sunday with a 6-2, 2-6, 6-4 victory over Jo-Wilfried Tsonga.

Making his 10th straight appearance at the season finale, Federer improved to a 35-7 event record with his sixth win in 10 meetings against Tsonga. Seven days ago, Federer also beat Tsonga in the BNP Paribas Masters final in Paris.

The 16-time Grand Slam champion looked ready for another comfortable win when he took the first set in 21 minutes, but Tsonga broke early in the second.

A closely fought third set ended when the pressure seemed to get to Tsonga. Trailing 5-4, he was broken at 15 and Federer chalked up his third straight win over the Frenchman since back-to-back losses at Wimbledon and Montreal.

"It's not always in your control when you play Jo," Federer said. "That's the beauty of it. I kind of enjoy that to some degree. But I think also partially because it was a first-round match, I think that's maybe why we saw some ups and downs from both players."

Federer will next play his great rival, Rafael Nadal, on Tuesday night.