Reigning two-time champion and six-time overall titlist Roger Federer and last week's Paris Masters champ David Ferrer were Tuesday's round-robin winners at the $7.125 million ATP World Tour Finals.

The second-seeded former world No. 1 Federer opened defense of his titles with a 69-minute 6-3, 6-1 spanking of helpless eighth-seeded Serb Janko Tipsarevic indoors at The O2 Arena. The mighty Federer was not broken in the predictable Day-2 affair, as Tipsarevic won only eight points on the Swiss' serve in the rout.

"I'm happy with my level of play today against Janko, who is obviously a good player," Federer said. "I think it's nice conditions here. I've had a good year. It's true, I feel like I'm striking the ball well after today. I hope it's a sign for more to come hopefully."

Federer is now 40-7 lifetime at this prestigious tournament, including titles from 2003-04, 2006-07, and the last two years. He was tied with Ivan Lendl for the most wins at this season-ending event prior to Tuesday.

Meanwhile, the fourth-seeded Ferrer won his 11th straight match by holding off sixth-seeded Juan Martin del Potro 6-3, 3-6, 6-4 in Tuesday's nightcap. Ferrer outlasted del Potro in 2 hours, 16 minutes, as he broke his Argentine counterpart three times, compared to two breaks for the loser.

In addition to his Paris victory last week, Ferrer also titled in Valencia in his native Spain last month.

Ferrer was an ATP Finals runner-up to Federer in 2007.

The 2009 U.S. Open champion and ATP Finals runner-up del Potro recently titled in Vienna and Basel, where he upended Federer in the final in the Swiss icon's hometown.

Wednesday's round-robin schedule will pit world No. 1 and Australian Open champion Novak Djokovic against third-seeded Andy Murray and fifth-seeded Czech Tomas Berdych versus seventh-seeded Jo-Wilfried Tsonga, who lost to Federer in last year's Tour Finals finale in London. The Olympic gold medalist Murray upended his good friend Djokovic in September's U.S. Open final.

Djokovic, who will finish as the year-end No. 1 for a second straight year, captured this elite eight-player event in Shanghai in 2008.

This week's four-player Group A features Djokovic (1-0), Murray (1-0), Berdych (0-1) and Tsonga (0-1), while Group B boasts Federer (1-0), Ferrer (1-0), del Potro (0-1) and Tipsarevic (0-1). The top-two players from each group will play in the semifinals on Sunday, and the winners will square off in the lucrative finale Monday in London.

The 2012 World Tour Finals champion can earn as much as $1.76 million.