CARLSBAD, Calif. (AP) - Top-seeded Vera Zvonareva of Russia beat countrywoman Vera Dushevina 6-3, 6-0 Thursday as the top five seeds advanced at the Mercury Insurance Open.
The third-ranked Zvonareva, who received a first-round bye, rebounded from a tough opening-round match to move into the quarterfinals. She will face the winner of the night match between No. 12 seed Sabine Lisicki of Germany and American teenager Coco Vandeweghe.
After a 6-4, 7-5 win in the second round Tuesday against American qualifier Jill Craybas, Zvonareva was pleased with her performance.
"I think I started off a little slow but then I think I picked it up and it was a little bit better, a little bit cleaner than the previous one," Zvonareva said.
No. 2 seed Andrea Petkovic of Germany and third-seeded Agnieszka Radwanska of Poland also advanced to the quarters with quick victories.
With the score tied 2-all, Petkovic won seven straight games to win the first set 6-2 and jump ahead 3-0 in the second when France's Virginia Razzano retired with a right shoulder injury.
Radwanska dispatched one of the three remaining American teenagers with a 6-1, 6-0 win over 19-year-old Christina McHale.
Fifth-seeded Ana Ivanovic advanced to a quarterfinal match against No. 4 seed Peng Shuai of China with a 6-1, 6-2 win against Italy's Alberta Brianti. Peng had to come from a set down and rally from a 1-3 hole in the third set to beat No. 16 seed Sara Errani of Italy 4-6, 6-2, 7-6 (7).
Daniela Hantuchova, the No. 8 seed from Slovakia, beat Zheng Jie of China, 6-2, 4-6, 6-4 and will meet Radwanska in the quarters.
In the only match not involving a seeded player, U.S. teenager Sloane Stephens was ahead 5-3 and had a set point when Tamira Paszek of Austria retired with a left abdominal injury. The 18-year-old Stephens next faces Radwanska in the quarterfinals.
Radwanska, the runner-up here last year, saw improvement over her opening-round match when she was pushed to a tiebreaker in a straight-set win over Elena Baltacha of Britain.
"I was very happy with my performance," Radwanska said. "I think I played much better than the first match. Everything was working."
Petkovic was sailing through her match when Razzano pulled out with her injury.
"The first two games I think we were both playing really well," Petkovic said. "I managed to hold onto that level and I don't know if was her injured shoulder or neck, but afterward she dropped her level. I managed to stay at the top level."