Second Seed Serena Williams Was Knocked Out of The China Open After a Thrilling 3rd-Round Battle Against Nadia Petrova on Thursday

World number one-elect Serena Williams has crashed out of the China Open, beaten in three sets by Russian Nadia Petrova just two days after reclaiming the top position.

Second seed Williams battled back several times but was unable to overcome the 13th seed, who reached the quarterfinals 6-4 3-6 7-6 in Beijing.

The 28-year-old Williams looked lethargic in the first set, with her ground strokes sailing long and her serve broken twice to hand her 27-year-old opponent the early lead.

But the American bounced back in the second, dictating play from the back oif the court to gain a break late in the set and even the match.

In the deciding third set, Williams missed a golden opportunity to pull ahead at 4-4, blowing three break points on Petrova's serve. However, she cranked up her serve to send it to a tiebreak.

Petrova took an early 5-2 lead, but Williams battled back one final time before the Russian could close it out.

Despite her defeat, Williams will take over the number one ranking from Russia's Dinara Safina when the WTA list is issued on Monday.

In other third round matches, seventh seed Vera Zvonareva of Russia, Polish 12th seed Agnieszka Radwanska and 14th seed Marion Bartoli of France all advanced.