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PARIS (AP) — So much for the thought that this might be the year Venus Williams would make a strong showing at the French Open.

So much for the thought that she and her younger sister Serena, the tournament's two top-seeded women, could deliver another all-Williams Grand Slam final.

Displaying little of the spark or strokes she regularly produces on grass and hard courts, and playing little like someone with the tour's best 2010 winning percentage, Williams stalled on the red clay of Roland Garros yet again Sunday, exiting in the fourth round with a 6-4, 6-3 loss to No. 19 Nadia Petrova.

"I don't think the conditions are always ideal here. ... You might not be used to it or you might not get a good bounce," said the No. 2-seeded Williams, who began the day 29-4 this season, including 15-2 on clay. "That's just the way this tournament goes."

For her, anyway. The American's seven major titles all came at Wimbledon or the U.S. Open, and only once has she made it to the semifinals in 14 French Open appearances — back in 2002, when she lost to Serena in the championship match.

Williams complained about the temperatures in the 50s and swirling winds that reached 15 mph, and wore a long-sleeved top over her much-discussed black lace dress. She didn't exactly heap praise on Petrova, now a win away from reaching her third French Open semifinal.

"I don't think she did anything super special," Williams said, "but she just played a little bit more consistently."

Actually, Petrova concurred with that assessment, calling her own play "solid."

"I came up with the good shots when it was necessary," she said. "That's it. I don't think I've done anything spectacular today."

Petrova will face No. 5 Elena Dementieva in an all-Russian quarterfinal. Dementieva ended the surprising stay of 131st-ranked qualifier Chanelle Scheepers, the first South African woman in the fourth round at Roland Garros since 1997, by winning 6-1, 6-3.

No. 3 Caroline Wozniacki of Denmark will play No. 17 Francesca Schiavone of Italy in another quarterfinal. Wozniacki, runner-up at last year's U.S. Open, scraped together a 7-6 (5), 6-7 (4), 6-2 victory over No. 14 Flavia Pennetta of Italy, and Schiavone eliminated No. 30 Maria Kirilenko of Russia 6-4, 6-4.

None of those encounters featured the big names or big-stage experience of the third-round match between four-time champion Justine Henin and Maria Sharapova, which resumed Sunday after being suspended because of darkness a night earlier.

Sharapova began the third set strongly, taking 11 of the first 15 points. But when facing an 0-2, love-40 deficit, Henin began playing more aggressively and swung the momentum, taking four consecutive games on the way to winning 6-2, 3-6, 6-3, her 24th consecutive victory at the French Open.

The Belgian will be forced to play for the fifth day in a row Monday, against No. 7 Samantha Stosur of Australia.

"I know it's going to be difficult," Henin said.

There was little suspense in men's action Sunday, although there was a mild upset: No. 15 Tomas Berdych of the Czech Republic beat No. 4 Andy Murray of Britain 6-4, 7-5, 6-3 to reach the French Open quarterfinals for the first time. Berdych now meets No. 11 Mikhail Youzhny of Russia, who advanced when No. 8 Jo-Wilfried Tsonga of France quit because of a hip injury.

Defending champion Roger Federer won in straight sets for the fourth consecutive round, dismissing No. 20 Stanislas Wawrinka 6-3, 7-6 (5), 6-2 in a matchup between buddies who paired up to win a doubles gold medal at the 2008 Beijing Olympics.

So does Federer wish he'd faced more adversity?

While acknowledging a test can have "its advantages," he said: "As long as you come through, I always say, it's a great tournament. I'm playing really well at the moment, so I'm very happy where my game is."

That could be bad news for his next opponent, No. 5 Robin Soderling of Sweden, who dispatched No. 10 Marin Cilic of Croatia 6-4, 6-4, 6-2. Tuesday's quarterfinal will be a rematch of the 2009 final, which is part of Federer's 12-0 mark against Soderling.

"Obviously, that's a good record to have," Federer said. "But because of the improvements he's made, he's an opponent not to underestimate."

The same might be said of Petrova, who was 0-4 previously against Williams, and had developed a reputation for having trouble closing out matches. But she derived confidence from two recent victories: against Serena on clay at Madrid this month, and against No. 15 Aravane Rezai in the third round at Roland Garros.

In the latter, Petrova wasted three match points before eventually coming through 10-8 in the third set, something the Russian called "a big step forward."

On Sunday, Petrova finished with a 22-15 edge in winners and saved six of the seven break points she faced. Most impressively, she steeled herself after getting broken to fall behind 2-0 in the second set.

"I kept my nerves calm," Petrova said.

For the most part. Two points from victory, she took aim at what appeared to be an easy overhead putaway. Instead, she shanked it off her racket's frame, sending the ball into the seats behind the baseline. A point later, Petrova netted a forehand.

Uh, oh.

But she recovered, and two points later, she smacked a forehand winner to end it.

Williams is still in the women's doubles tournament with her sister, but it seems likely that her participation in this French Open will be remembered more for a sartorial statement than any spectacular strokes.

Even Petrova weighed in.

"I must say: The dress that Venus wore — you must have a little guts to do that," she said.

Williams designed the corset-like outfit that drew so much attention, and said she'll "retire" it after this event. That doesn't mean she won't come up with something else buzz-worthy.

"Each and every day, on and off the court, on the match court and the practice court, I'm always pushing the envelope," Williams said. "But, you know, I have to wait until next year."

A familiar refrain for her at Roland Garros.