Radwanska, ranked No. 39, has five top-20 wins this season after defeating 16th-ranked Jankovic.
Joe Scarnici/Getty Images

CARLSBAD, Calif. (AP) -- Poland's Ursula Radwanska took advantage of Jelena Jankovic's poor serving for a 6-2, 4-6, 6-3 victory Thursday in the second round of Southern California Open.

The sixth-seeded Jankovic, from Serbia, served up seven double faults and was successful on only 59 percent of her first serves as Radwanska advanced to the quarterfinals against top-seeded Victoria Azarenka of Belarus. It is just the fourth time this season Radwanska has reached the quarters.

Radwanska, ranked No. 39, has five top-20 wins this season after defeating Jankovic, ranked 16th.

Wild-card entrant Virginie Razzano of France also advanced with a 6-1, 6-4 victory over eighth-seeded Carla Suarez Navarro of Spain. Razzano, who beat two-time Grand Slam singles champ Svetlana Kuznetsova of Russia in the first round, will face third-seeded Petra Kvitova of the Czech Republic.

Copyright 2014 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

SI Apps
We've Got Apps Too
Get expert analysis, unrivaled access, and the award-winning storytelling only SI can provide - from Peter King, Tom Verducci, Lee Jenkins, Seth Davis, and more - delivered straight to you, along with up-to-the-minute news and live scores.