Italy's Sara Errani ended the French resistance at the Pan Pacific Open, rallying to defeat ninth seed Marion Bartoli 3-6 6-2 6-2 to reach the last eight of the WTA premier five event on Wednesday.
The sixth seed finally overcame Bartoli after two hours and 22 minutes, clinching victory with a crunching forehand her opponent could only dump into the net.
"I'm a bit tired but I have lots of motivation to keep winning," said Errani, who has captured titles in Acapulco, Barcelona, Budapest and Palermo this year.
"It's been an amazing year but I still have to qualify for the (season-ending) Championships."
Errani set up a quarter-final against Russia's Nadia Petrova, the 17th seed battling to a 7-6 6-7 6-4 victory over Croatia's Petra Martic.
Last year's US Open champion Samantha Stosur, seeded eighth, also booked her place in the last eight with a 6-4 7-5 win over Slovakia's Dominika Cibulkova.
Nine of the world's top 10 women are competing at the event, with US Open champion Serena Williams the only absentee among the WTA's elite.