Carson, CA (My Sportsbook) - China's Zheng Jie pulled off a shocker Thursday night, toppling world No. 1 and defending champion Dinara Safina in three sets to advance to the quarterfinals at the $700,000 LA Women's Tennis Championships, a US Open Series event.

The 26-year-old Zheng, who is currently ranked 23rd in the world and is seeded 14th at this week's tournament, scored a 7-5, 4-6, 6-4 victory in a match that lasted 2 hours, 10 minutes. Zheng not only beat Safina for the first time in five lifetime meetings, but also moved a step closer to her first title since 2006.

Zheng will take on surging 13th-seeded Aussie Samantha Stosur, who took out sixth-seeded Serb Ana Ivanovic 6-3, 6-2. Ivanovic is a former No. 1 and former French Open champ.

As for Safina, the French Open and Aussie Open runner-up who beat Italian Flavia Pennetta in last year's finale here, Thursday marked just her 10th loss in 58 matches this year.

Second-seeded Russian Vera Zvonareva was a third-round winner Thursday as she outlasted rising Belgian Yanina Wickmayer 7-6 (7-5), 4-6, 6-4 on the hardcourts at The Home Depot Center.

Up next for Zvonareva will be last year's LA runner-up Pennetta. The 10th- seeded Pennetta posted a Day-4 upset by ousting fifth-seeded Russian Nadia Petrova 6-3, 6-3.

Meanwhile, eighth-seeded Pole Agnieszka Radwanska routed struggling Russian Anna Chakvetadze 6-3, 6-2.

Also, Russian Maria Sharapova defeated Alona Bondarenko of the Ukraine, 4-6, 6-0, 6-3.

A couple of injuries were factors in matches Thursday. China's Li Na, the 12th seed, withdrew from her third-round match against Poland's Urszula Radwanska due to a right knee injury. Also, Romanian Sorana Cirstea was ahead 6-3, 1-0 on Sabine Lisicki when the 17th-seeded German retired due to a right shoulder problem.

Cristea will play Agnieszka Radwanska on Friday, while Sharapova battles Urszula Radwanska.

The 2009 LA champ will take home $107,000.