ROME -- What was once almost unthinkable in tennis now happens more and more often: Roger Federer loses.
The latest defeat came Friday, a 7-6 (7-4), 7-6 (9-7) decision to 27th-ranked Radek Stepanek in the Rome Masters quarterfinals.
This was Federer's sixth loss of the year. The top-ranked Swiss lost only nine matches in all of 2007.
"Usually when I have a lead I don't let it go, so it's quite disappointing," Federer said. "I played so poorly on the big points."
Federer piled up a string of defeats at the beginning of this year when he was diagnosed with mononucleosis. He won his first title of 2008 at the Estoril Open last month, the longest he's waited in nine years.
"He definitely doesn't have the results he was used to in previous years," Stepanek said. "But the other players are getting better. I came to the match with the belief that I can win."
The Czech celebrated his victory by writhing like a caterpillar, with his belly on the clay.
After only nine losses in all of '07, Roger Federer already has six this year.
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"That was the way I celebrated the first tournament victory of my career," he said. "Everyone was asking me when I would do it again, but I was waiting for the right occasion, and today was special."
In the semifinals, Stepanek will face Australian Open winner Novak Djokovic. He advanced when Nicolas Almagro retired with an apparent wrist problem while the Serb led 6-1, 1-0.
Federer's defeat follows that of three-time defending champion Rafael Nadal. The Spaniard was beaten in the second round by Juan Carlos Ferrero.
"It shows how the (other) players are getting better. Everybody is hungry," Stepanek said. "Two players can't win all the tournaments."
The Rome Masters is a clay-court tuneup for the French Open, which begins May 25. Roland Garros is the only Grand Slam Federer has never won. He has also never won a title in Rome. Last year, Federer was upset in the third round by Italian wild card Filippo Volandri.
In the other half of the draw, sixth-seeded Andy Roddick eliminated No. 14 Tommy Robredo 6-3, 4-6, 7-6 (7-4) to match his best performance in Rome.
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