Serena Williams trips in quarters

~ Federer wasted little time advancing to the semifinals.

PARIS -- Serena Williams, of all people, got a case of the jitters.

That was her explanation, anyway.

The 10-time Grand Slam champion kept finding herself in, then out of, trouble in the French Open quarterfinals Wednesday, until running out of stamina and strokes down the stretch of a 7-6 (3), 5-7, 7-5 loss to Svetlana Kuznetsova that ended Williams' 18-match winning streak at major tournaments.

"I had an opportunity, and I got really tight, and I pretty much gave it to her," said the second-seeded Williams, who blew a 3-1 lead in the third set. "It was like, 'Here. Do you want to go to the semis? Because I don't.' She was like, 'OK.'"

The seventh-seeded Kuznetsova's semifinal opponent today is No. 30 Samantha Stosur of Australia, who defeated Sorana Cirstea of Romania 6-1, 6-3. The other women's semifinal is No. 1 Dinara Safina of Russia against No. 20 Dominika Cibulkova of Slovakia.

If Stosur-Cirstea was as onesided as could be, Kuznetsova-Williams was hyper-competitive and superbly played. Until, at least, Kuznetsova took eight of the last nine points, breaking Williams in the final game.

Williams denied she felt fatigued, blaming nerves instead.

How could that be?

"Maybe I put some expectations on myself that I didn't put on myself initially," she said.

Roger Federer spoke about dealing with nerves Wednesday, too, although his problems came before he began playing 11th-seeded Gael Monfils of France.

"We're all nervous at this stage of the competition," said Federer, who knows this might be his best chance to win the only Grand Slam tournament missing from his resume. "I felt it. Yesterday I felt it, and I felt it again today in the warmup. I was tired, I was nervous, and I didn't feel really good. Then once out on court, you know, I get my act together."

There's an understatement.

Federer beat Monfils 7-6 (6), 6-2, 6-4 to close in on completing a career Grand Slam and earning a 14th major title to tie Pete Sampras' career record.

Next up for Federer is No. 5 Juan Martin del Potro of Argentina, who eliminated No. 16 Tommy Robredo in straight sets. Friday's other men's semifinal will be No. 23 Robin Soderling -- the man who upset four-time defending champion Rafael Nadal in the fourth round -- against No. 12 Fernando Gonzalez.