PARIS // Last year's runner-up Sam Stosur was knocked out of the French Open on Friday, losing to Gisela Dulko 6-4, 1-6, 6-3 less than an hour after defending champion Francesca Schiavone became the first player to reach the fourth round.
Top-ranked Caroline Wozniacki will also have to wait for her first major title after losing to Daniela Hantuchova 6-1, 6-3 in the third round.
The Dane has been No 1 in the WTA rankings for almost the entire season but never really challenged her Slovak opponent on Court Suzanne Lenglen, having her serve broken five times.
This is the first time in the Open era that the top two seeded women failed to make the round of 16 at a grand slam tournament. No 2 Kim Clijsters lost Thursday.
Stosur struggled early but then easily won the second set to take back control against Dulko.
But the 51st-ranked Argentine put herself back in the match by breaking to take a 4-2 lead in the third. Dulko then held twice to advance. Roger Federer had no such worries.
The 2009 French Open champion had 10 aces and only 20 unforced errors in a 6-1, 6-4, 6-3 win over No 29 seed Janko Tipsarevic.
Later Friday, Novak Djokovic is scheduled to put his perfect season on the line against 2009 US Open champion Juan Martin del Potro.
The eighth-seeded Stosur, who also reached the semi-finals at Roland Garros in 2009, had 35 unforced errors in the match on Court Philippe Chatrier.
Dulko matched her best grand slam result by reaching the fourth round. She also won three matches at the 2006 French Open and the 2009 US Open.
Schiavone was broken at the beginning of her match, but then won five straight games to take the first set and eventually the match when opponent Peng Shuai of China retired while trailing 6-3, 1-2.
Peng called for a doctor after the first game of the second set and had her blood pressure checked. She looked exhausted in her chair and then started to cry but broke for a 2-0 lead.
Schiavone won the next game before her opponent quit. She will face the 10th-seeded Jelena Jankovic next after the Serb progressed with a 6-2, 6-2 win over Bethanie Mattek-Sands of the United States.
"I've been just sick for three or four days," Peng said, adding that she has had a fever. "So it's tough for me to play. I was really tired. I was really sick so my body could not really handle that."
Svetlana Kuznetsova, the 2009 French Open champion, advanced by beating Rebecca Marino of Canada 6-0, 6-4. Seventh-seeded David Ferrer also won, beating No. 31 Sergiy Stakhovsky of Ukraine 6-1, 6-1, 6-3.
* Associated Press