Federer reaches Tour Finals semis

Six-time champion Roger Federer secured a semifinal berth at the season-ending ATP World Tour Finals.

The second-seeded former No. 1 got past gritty fourth-seeded Spaniard David Ferrer 6-4, 7-6 (7-5) in a rematch of the 2007 final, which was also won by the Swiss icon, in Shanghai.

Federer prevailed in 1 hour, 48 minutes by being broken only once on Day 4 against Ferrer, who owns an ATP-best seven titles this season. Federer is now 14-0 lifetime against Ferrer, who has won only three sets in 10 years while playing the Swiss superstar.

The 31-year-old Federer has now reached at least the semis at this exclusive event 10 times in 11 tries. He's seeking a third straight title in the elite eight-player tournament, which he captured back-to-back in 2003 and 2004, 2006 and 2007, and the last two years.

"I've been very successful over the years. Probably won most titles indoors, maybe more than all the other guys combined," Federer said. "But that doesn't make me the best this week."

Also on Thursday in London, sixth-seeded Juan Martin del Potro handled eighth- seeded Serb Janko Tipsarevic 6-0, 6-4 in 76 minutes at The O2 Arena. The overmatched Tipsarevic was unable to break the formidable Argentine, who has won 12 of his last 14 matches on tour, including titles in Vienna and Basel last month.

Del Potro was the 2009 Tour Finals runner-up.

Friday's round-robin play will pit top-ranked Australian Open champion Novak Djokovic against fifth-seeded Tomas Berdych and world No. 3 U.S. Open and Olympic titlist Andy Murray versus seventh-seeded Jo-Wilfried Tsonga. Djokovic captured a Tour Finals title in 2008 in Shanghai, while Tsonga was last year's runner-up to the amazing Federer.

This week's four-player Group A features Djokovic (2-0), Murray (1-1), Berdych (1-1) and Tsonga (0-2), while Group B boasts the 17-time Grand Slam winner Federer (2-0), Ferrer (1-1), del Potro (1-1) and Tipsarevic (0-2). 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.