Petrova tops S.Williams at China Open

BEIJING, Oct. 8 (UPI) -- Nadia Petrova won a third-set tiebreaker Thursday for a third-round upset of world No. 2 Serena Williams at the $4.5 million China Open in Beijing.

Williams was coming off a second-round win that assured her of returning to the No. 1 spot in the world rankings, but Petrova outlasted Williams 6-4, 3-6, 7-6 (7-5). It was only the second time in eight career meetings that Petrova beat Williams.

There were no service breaks in the third set but Petrova built a 5-1 lead in the tiebreaker. Williams fought back to 5-4 before Petrova closed out the match.

Seventh-seeded Vera Zvonareva got by No. 10-seeded Flavia Pennetta 6-3, 5-7, 7-5 and goes against 14th-seeded Marion Bartoli, who defeated Zhang Shuai 6-1, 6-4 Thursday, in the quarterfinals.

No. 12-seeded Agnieszka Radwanska rallied for a 4-6, 6-4, 6-2 win over Maria Jose Martinez Sanchez and draws the tournament's highest remaining seed, No. 4 Elena Dementieva, in Friday's quarterfinals.

The other quarterfinals send Petrova against Peng Shuai, a local favorite who upset Jelena Jankovic and Maria Sharapova this week, and No. 6-seeded Svetlana Kuznetsova against Anastasia Pavlyuchenkova.

The China Open concludes Sunday with a title match worth $775,500 to the champion.