PARIS — Venus Williams’ celebrated corset went under wraps today, and now it’s out of the French Open.

Playing with a long-sleeve top over her black lace outfit on a chilly afternoon, Williams lost in the fourth round to Nadia Petrova, 6-4, 6-3.

Williams came into the tournament seeded No. 2 behind her sister Serena, but Petrova spoiled the possibility of a sibling showdown in the final.

Petrova has been a nemesis for the Williams family lately – she beat Serena in the third round at Madrid less than three weeks ago.

Justine Henin rallied in a winner-take-all set that seemed like a final, outslugging Maria Sharapova 6-2, 3-6, 6-3. The two former No. 1s returned to center court following an overnight suspension of the third-round showdown after two sets.

In men’s play, top-ranked Roger Federer reached the quarterfinals in his bid for a second successive title, beating Olympic doubles partner Stanislas Wawrinka 6-4, 7-6 (5), 6-2.

On a damp, windy afternoon, Williams and Petrova bundled up. Only the flounce of Williams’ buzz-generating corset was visible, while Petrova wore long sleeves and tights under a frilly skirt.

Petrova controlled rallies with steady play from the baseline and finished strong, a problem for her in the past. Petrova swept the final four games and wobbled only once, shanking an overhead when leading love-30 in the final game.

She collected herself and won the final two points, closing out the match with an emphatic forehand winner.

Serena wore her playing outfit while watching her sister’s defeat from the stands. They were to team up in a doubles match later today.

Venus converted only 1 of 7 break-point chances. In the second set she lost serve three times after taking a 2-love lead.

Petrova, seeded 19th, is a two-time semifinalist, but she’s into the quarterfinals for the first time since 2005. The victory was her first against Williams in their five meetings.

Williams came into the tournament with the best record this year on the women’s tour, but tricky footing has always made clay her worst surface. In 14 French Open appearances, she reached the semifinals only once – in 2002, when she lost to her sister in the final. She has advanced beyond the fourth round just once in the past six years.

Joining Petrova in the quarterfinals were No. 3 Caroline Wozniacki, No. 5 Elena Dementieva and No. 17 Francesca Schiavone.

Wozniacki, enjoying her best run at Roland Garros, needed three hours to beat No. 14 Flavia Pennetta 7-6 (5), 6-7 (4), 6-2. No. 5 Elena Dementieva beat unseeded Chanelle Scheepers 6-1, 6-3. No. 17 Francesca Schiavone defeated No. 30 Maria Kirilenko 6-4, 6-4.

Henin and Sharapova played the seesaw final set after the match was suspended late Saturday because of darkness. The pivotal moment came when Henin fell behind 0-2, love-40, then overcame four break points to hold.

She soon led 4-2, broke to go ahead 5-3 and served out the victory.

“I kept my chances to win this tournament,” said the four-time champion, playing at Roland Garros for the first time since 2007. “I will give my best and enjoy it. It was a really good test.”

The victory extended Henin’s winning streak at Roland Garros to 24 matches. It was the first meeting between the two rivals since Henin spent 20 months in retirement before mounting a career comeback this year.

Henin next plays No. 7 Sam Stosur.

Walking onto center court to resume play after a 15½-hour interruption, Henin smiled slightly. Sharapova followed wearing a scowl, and that intensity carried over when play began.

Sharapova pumped her fist after almost every point she won – and often before points. Henin found herself on the defensive at first, then began sending shots into the corners, forcing Sharapova to hit on the run.

“(At) the beginning I felt like I was the one that was more aggressive,” Sharapova said. “That kind of changed a little bit. She started being a little bit more aggressive, and she started feeling much better about her game.”

Federer struggled with the wind at times and fell behind 4-2 in the second set, but the No. 20-seeded Wawrinka couldn’t hold the lead and missed an easy volley at 5-all in the tiebreaker.

When Wawrinka lost the set he mangled his racket, and Federer quickly pulled away after that. The defending champion has won all 12 sets he’s played so far.

“I’m happy with the way things are going,” Federer said. “I’m serving well, I’m moving well. Everything is fine.”