STANFORD, Calif. -- Top-seeded Agnieszka Radwanska beat Francesca Schiavone 6-4, 6-3 on Wednesday night in the second round of the Bank of the West Classic.
Radwanska, the Polish star ranked No. 4 in the world, won for the 10th time in her last 13 matches to improve to 34-10 this year. She won a career-high 59 matches last season.
Italy's Schiavone, ranked 59th, entered the event on a three-match skid, but beat former Stanford All-American Mallory Burdette in her first match.
Radwanska beat Schiavone a fourth straight time to even the series at 4-4. They were playing for the first time in two years.
Earlier, fifth-seeded Sorana Cirstea beat American Coco Vandeweghe 6-3, 6-3 and No. 6 Varvara Lepchenko advanced with a 6-4, 6-4 victory over Austria's Tamira Paszek.
The 32nd-ranked Cirstea, Romania's second-ranked player, reached the semifinals last year. She'll meet unseeded Olga Govortsova in the quarterfinal. Govortsova upset second-seeded Samantha Stosur.
"I'm happy to be back," Cirstea said. "I played well here last year and have many good memories. It's a good start to what is to come."
Vandeweghe, who reached the final last year, went through qualifying to gain a spot in the main draw.
"It's not easy to play her," Cirstea said. "She serves big and has a big game. You have to be there every single point."
The 40th-ranked Lepchenko reached her second quarterfinal of the season. The American will face Radwanska.
"I hope to play better in each match," Lepchenko said. "I'm going to focus on the things I need to do to play well on the big stages."