Second seed Caroline Wozniacki recovered from a second-set hiccup to move into the quarter-finals of the Indian Wells WTA tournament with a 6-3, 3-6, 6-0 victory over Russian Nadia Petrova on Tuesday.
The 19-year-old Dane, the youngest player left in the draw, broke her opponent three times in the final set to wrap up victory in one hour 47 minutes.
"It was a match where it just went up and down quite a bit," Wozniacki told reporters after setting up a quarter-final with China's Zheng Jie.
"You didn't really know what to expect. It was not really a great rhythm there and I didn't feel the ball as well.
"But I'm just happy that I fought through and I won the match. That's the most important thing. I just think that I will be more ready for the next match," she added.
Zheng, a surprise semi-finalist at the Australian Open in January before losing to former world number one Justine Henin, reached the last eight by beating Australia's Alicia Molik 6-3, 4-6, 7-6.
Fourth-seeded Russian Elena Dementieva and Poland's Agnieszka Radwanska, the fifth seed, each advanced in relatively comfortable fashion at the Indian Wells Tennis Garden.
Dementieva cruised through with a 6-3, 6-3 win against Frenchwoman Aravane Rezai and will next meet Radwanska, who crushed 11th seed Marion Bartoli of France 6-3, 6-2.
"Today was pretty comfortable for me because she was playing like I expected her to play," Dementieva said after clinching victory over Rezai in just over an hour.
"She was very aggressive, hitting some flat balls, and it was easy to get to the rhythm.
"We have played lots of times before and I knew what to expect from her, so it was not a big problem today."
Asked to assess her quarter-final match against Radwanska, Dementieva replied: "I feel like it's on my game, you know. I need really to create something. I need to go for the winner.
"It's not like I'm going on the court and I'm patient, because there's nothing to be waiting for. She doesn't make any mistakes. She moves well. She has a very smart game.
"It's going to be up to me, if I will be able to step forward, take advantage of the short ball and be aggressive the whole match."
In other matches, sixth-seeded Serb Jelena Jankovic eased past Israel's Shahar Peer 6-2, 6-2 and eighth-seeded Australian Samantha Stosur eliminated holder Vera Zvonareva of Russia 6-2, 7-5.