Updated

Reigning two-time champion and six-time overall titlist Roger Federer was an easy round-robin winner Tuesday at the $7.125 million ATP World Tour Finals.

The second-seeded former world No. 1 superstar 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 the 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.

Later Tuesday, fourth-seeded David Ferrer, fresh off his Paris Masters title last week, will battle surging sixth-seeded Argentine slugger Juan Martin del Potro. Ferrer was an ATP Finals runner-up to Federer in 2007. Del Potro has titled in two of his last three events.

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 back 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, del Potro 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.