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Gritty Spaniard David Ferrer upended robin play at the $3.5 million ATP World Tour Finals.

The fifth-seeded Ferrer surprised the world No. 3 star Murray in 6-4, 7-5 fashion on the indoor hardcourt at The O2 arena in London. Ferrer rallied from a break down in the second set to prevail in exactly two hours, as he broke Murray on five occasions, compared to three breaks for the three-time Grand Slam runner-up from Scotland.

The 2007 Tour Finals runner-up Ferrer is 1-0 in this week's four-player Group A, while the 2011 Australian Open runner-up Murray dropped to 0-1.

Monday's other Group A match will pit world No. 1 Novak Djokovic (0-0) against seventh-seeded Czech Tomas Berdych (0-0). The reigning U.S. Open, Wimbledon and Aussie Open champion Djokovic captured this prestigious season-ending tournament in 2008.

The high-flying Djokovic owns a tour-best 10 titles on the circuit this season.

This exclusive event features only the top-eight players in the world. The four-player Group B is comprised of second-seeded Rafael Nadal (1-0), fourth- seeded Roger Federer (1-0), sixth-seeded Jo-Wilfried Tsonga (0-1) and eighth- seeded American Mardy Fish (0-1). The five-time Tour Finals titlist Federer defeated his great rival and fellow former No. 1 Nadal in last year's finale in London.

Nadal and Federer will lock horns at The O2 on Tuesday. The Spaniard topped the Swiss in this year's French Open final.

Federer is tied with Pete Sampras and Ivan Lendl for the most titles at this prestigious tournament.

The 16-time Grand Slam champion Federer has been the hottest player of late, as he entered this event with a 12-match winning streak. He beat Tsonga for the Paris Masters crown two weeks ago and titled in his native Basel the week before that.

Round-robin play will be staged through Friday in London, while the semifinals will be held on Saturday and the lucrative final on Sunday. The top-two finishers from each group will play in the semis.

This week's big winner will earn at least $770,000. An undefeated champion would pocket $1.63 million.