PARIS — For Serena Williams, missed chances came in a flurry Friday at the French Open.

She shanked overheads, hit wild volleys and squandered seven break points. The net result: a stunning third-round loss to Katarina Srebotnik, 6-4, 6-4.

The hasty exit matches Williams' earliest in nine visits to Roland Garros and guarantees a first-time women's champion. Williams, who won the French Open in 2002, was the lone former champion to enter the draw.

"I missed a lot of easy shots and a lot of key points that I felt like could have turned the match around," a subdued Williams said shortly after the loss. "I wasn't able to capitalize."

Three-time defending champion Rafael Nadal played for the fourth consecutive day in the rain-interrupted tournament and defeated Jarkko Nieminen 6-1, 6-3, 6-1 in the third round.

Nadal, who was bothered this spring by a blister on his right foot, won easily despite needing treatment of the foot by a trainer after the second set.

The 27-year-old Srebotnik earned the biggest victory of her career. She has only one win over a player ranked higher than the No. 5-ranked Williams, beating No. 4 Amelie Mauresmo at Zurich in 2005.

No. 1-seeded Maria Sharapova and No. 2 Ana Ivanovic advanced. In the completion of a second-round match halted in the second set Thursday because of darkness, Sharapova beat American Bethanie Mattek 6-2, 3-6, 6-2. Ivanovic reached the fourth round by beating 17-year-old Caroline Wozniacki 6-4, 6-1.

Williams, who played the day's first match on Court Suzanne Lenglen, converted only one of eight break-point chances and was 0-for-6 in the second set. She repeatedly set up points well but failed to finish them, losing 14 of 21 points at the net.

"There are a lot of things I would try to do different, but you can't rewind time," said Williams, who also lost in the third round in 1999.

Her mother and coach, Oracene Price, said Williams has "been in a funk. It's not like her. She wasn't herself."

In the final game of the first set, Williams dumped an easy overhead into the net. Four points later, she worked her way forward but blew a volley, then bent over in dismay and pressed her forehead against the tip of her racket handle.

Another botched overhead cost her in the sixth game of the second set, helping Srebotnik to reach 3-3.

"I wasn't nervous," Williams said. "She was getting a lot of balls back, and I might have let that get into my head. She was just making some shots I don't think she's ever made before, or she probably would be in the top two."

When Williams fell behind she turned up the volume, grunting with almost every shot and screaming in celebration when she hit a winner. But she was unable to rally, and the No. 27-seeded Srebotnik kept her cool down the stretch.

"Today I woke up and it was just another opportunity," Srebotnik said. "This is what you work so hard for — to be in third round where you play Serena or someone like that and you have really nothing to lose."

Srebotnik credited her tactics for the upset, mixing the pace of her ground strokes to keep Williams off balance.

"That was the rhythm that I was trying ... to get her on a wrong foot and stuff like that," Srebotnik said. "When she's serving well, she's very tough, but once I got in the rally I had no problem playing her."

In the second set, Williams hit an ill-advised drop shot into the net to lose serve and fall behind 5-4. She saved two match points in the next game, but on the third yanked a forehand wide for her 25th unforced error, then met Srebotnik at the net with a grin and handshake.

Williams sat dejected at her postmatch news conference, explaining her demeanor by saying, "I just don't want to be here."

No. 11 Vera Zvonareva beat Stephanie Cohen-Aloro 6-4, 6-2. In the completion of a second-round match, No. 25 Nadia Petrova swept Alisa Kleybanova 6-3, 6-3.

Sharapova won despite 10 double-faults, giving her 27 in two matches. She finished with 51 unforced errors as she struggled to find a comfort level on clay, her least-favorite surface.

The French Open is the only Grand Slam she has yet to win.

"You're going to have to hit more balls, and you're going to have to move a few extra steps to the ball," Sharapova said. "You have to be more patient. I'm definitely getting better at that, and I'm getting smarter out there."