Second-seeded Marion Bartoli won the last 11 games to surge past unranked US university player Mallory Burdette 7-5, 6-0 in the second round of the WTA hard-court tournament here.
France's Bartoli lost only seven points on her serve in the second set on Thursday as she recovered from 4-1 down in the opening frame against the player who attends Stanford University, where the tournament is held.
Burdette had two chances to take the first set, but couldn't covert either one and Bartoli seized the chance to turn the tide.
"She was playing well at the start," said Bartoli, who won the title in 2009 and was runner-up last year to Serena Williams. Bartoli was also runner-up here in 2008.
"She was hitting the lines and the corners. It was not easy to come back. I had to wait for the storm to calm," Bartoli said.
"I needed to take the momentum away from her. I stepped up and played harder. I tried to get more first serves in.
"I had the momentum going into the second set. But I knew it would not be easy until the last point, I didn't want it to slip away."
Bartoli converted five of her 13 break chances against her inexperienced opponent, firing 26 winners with 17 unforced errors.
"My experience paid off and helped me a lot," said the world number 10. "I have good memories here. I was not worried, I knew I could come back."
Bartoli next faces fifth-seeded Belgian Yanina Wickmayer in Friday's quarter-finals, when top-seeded Williams, fresh from her triumph at Wimbledon, will take on sixth-seeded Chanelle Scheepers of South Africa.
Third seed Dominika Cibulkova beat Japanese qualifier Erika Sema 6-1, 6-3 while unseeded Urszula Radwanska, sister of Wimbledon runner-up Agnieszka Radwanska, survived a second-set wobble to defeat eighth-seeded New Zealander Marina Erakovic 6-3, 3-6, 6-4.
Poland's Radwanska was up a set and a break but said she lost focus as Erakovic battled back to knot the match at one set apiece.
"And she also started playing better," said Radwanska, who won a match here last year as a qualifier.
But the younger Radwanska, ranked 57th in the world, held on to wrap up the match in just over two hours. She booked a quarter-final clash with American Coco Vandeweghe.
Romanian Sorana Cirstea reached her fourth quarter-final of 2012 with a 6-3, 6-3 victory over China's Zheng Saisai, advancing to a clash with Cibulkova.