Williams, playing for the first time since losing to her sister in the championship match at Wimbledon, finally prevailed over qualifier Michelle Larcher de Brito 4-6, 6-3, 6-2.

Williams served 14 aces in a match that lasted an hour, 46 minutes. This was only the fourth tournament of the year for de Brito.

In the quarterfinals, Williams will take on the winner of Thursday's match between Patty Schnyder and Alisa Kleybanova. Williams has won three tournaments this year, those victories coming in succession while she posted an 18-match winning streak.

Second-seeded Anna Chakvetadze also advanced with a 6-3, 6-4 decision over Shahar Peer and Ai Sugiyama was a surprising 6-3, 6-1 winner over fourth-seeded Daniela Hantuchova.

Sugiyama set up a quarterfinal meeting with Dominika Cibulkova, who continued her unexpected run in the tournament with a 6-2, 6-3 win over Kateryna Bondarenko.

Cibulkova ousted seventh-seeded Nadia Petrova on Tuesday.