France's Julien Benneteau scored the biggest upset of this week's ABN AMRO World Tennis Tournament in Rotterdam, knocking off top seed and world No. 2 Roger Federer 6-3, 7-5 Friday in the quarterfinals.

Benneteau, who is ranked No. 39 and has never won an ATP Tour singles title, caught the Swiss great on an off day to score one of the biggest victories of his career.

The 39th-ranked Frenchman showcased an especially effective return game, winning two-thirds of Federer's second-serve points and breaking the Swiss great's serve five times.

Friday's win was Benneteau's second over Federer in six matches, the other having come at the 2009 Paris Masters. Federer had won their two previous contests, both played last year on grass.

Federer - winner of this Netherlands indoor hard-court event in 2005 and 2012 - had not lost before the semifinals since last year's U.S. Open, when he was eliminated in the quarterfinal stage by Czech Tomas Berdych.

The 17-time Grand Slam champion has not lost prior to the quarterfinals since a third-round defeat to American Andy Roddick at last year's Miami Masters.

In Saturday's semifinals, Benneteau will take on the winner of Friday's late match between countryman Gilles Simon and Slovak Martin Klizan.

The other semifinal will pit second-seeded Argentine Juan Martin del Potro against Bulgaria's Grigor Dimitrov. EFE