World number two Williams battled back several times but was unable to overcome Russian 13th seed Nadia Petrova, who won in three sets, 6-4, 3-6, 7-6 (7/5). The 28-year-old Williams looked lethargic in the first set, with her ground strokes sailing long and her serve broken twice to hand the 27-year-old Russian the early lead. But the American bounced back in the second, putting a bit more pace on her shots and dictating play from the backcourt 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. But 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 the loss, Williams will nevertheless take over the number one ranking from Russia's Dinara Safina when the new WTA list is issued on Monday.