Samantha Stosur beats Li Na

MASON, Ohio -- Serena Williams' premature departure from the Western & Southern Open could pay big dividends for Samantha Stosur.

Stosur, capitalizing on an unexpected day of rest, returned to the court Thursday and upset fifth-seeded Li Na of China 6-4, 3-6, 6-4 in the U.S. Open tuneup.

The 10th-seeded Australian was scheduled to face Williams on Wednesday in the round of 32 before Williams withdrew after aggravating a right big toe injury.

"I wasn't complaining that (Williams) pulled out," said Stosur, who lost to Williams in the finals at Toronto last week. "I had a pretty easy day, which was nice, considering the week I had before. So I guess that was good for today's match and hopefully will be good for tomorrow."

Stosur has beaten Li -- the French Open champion -- three times this season, including in the same round last week at Toronto.

Stosur became the first woman to reach the quarterfinals. Slovakia's Daniela Hantuchova followed when she upset eighth-seeded Marion Bartoli 6-3, 5-7, 6-3. Hantuchova improved to 5-1 all-time against Bartoli. Second-seeded Vera Zvonareva of Russia also advanced to the quarterfinals with a 6-2, 6-2 win over Petra Martic, as did fourth-seeded Maria Sharapova, who beat Svetlana Kuznetsova 6-2, 6-3.

Also Thursday, ninth-seeded German Andrea Petkovic beat No. 6 Petra Kvitova of the Czech Republic 6-3, 6-3; No. 13 Jelena Jankovic of Serbia held off seventh-seeded Italian Francesca Schiavone 6-3, 5-7, 6-4; and No. 16
Peng Shuai of China beat Israel's Shahar Peer 6-3, 6-2.

The bracket is wide open because of injuries and upsets. In addition to Serena Williams withdrawing, defending champion Kim Clijsters (injuries) and Venus Williams (virus) had to skip the tournament.

Top-ranked Caroline Wozniacki was upset in her first match of the tournament, and third-seeded Victoria Azarenka withdrew because of an injured hand.

Information from The Associated Press was used in this report.