LONDON, Nov. 20 (Xinhua) -- World No. 4 Roger Federer defeated Frenchman Jo-Wilfried Tsonga 6-2, 2-6 and 6-4 in his opening match at the ATP World Tour Finals on Sunday.

Federer, 30, dominated the first set by breaking twice, but made more errors in the second set, giving Tsonga chances to make revenge. In the final set, the defending champion waited until the tenth game to break, grabbing the first win at the O2 Arena this year.

"I thought I wasn't playing that poorly," said the 16-time Grand Slam champion Federer. "You just try to stay calm. Absolutely it's not always in your control when you play Jo. That's the beauty of it. I kind of enjoy that to some degree."

The Swiss master lost to Tsonga in the last 16 round at the Wimbledon Championships this year, but beat the French No. 1 later in the quarterfinals at the US Open.

As a debutant in the year-ending tournament, Tsonga said he didn't feel extra pressures. "I was okay. But like the last time, I started really bad and then it's difficult."

In the Paris Masters last week, Federer outplayed Tsonga 6-1, 7- 6(3) to clinch the title.