Despite complaining that her ankle has been bothering her for a while, top seed Victoria Azarenka, unbeaten in 17 matches this season, remained on course in her title defense at the BNP Paribas Open by cruising into the last eight with a 6-3 6-1 victory over Urszula Radwanska, while Urszula's more successful sister Agnieszka Radwanska was the only upset of the day, as the third seed fell to seed No.13 Maria Kirilenko. After quickly losing the first set, Agnieszka fought back to win the second and go 3-1 up in the third, before Kirilenko won four straight games for a 5-3 lead and a 6-1 4-6 7-5 victory after a small slump.
Maria Sharapova won a close opening set against Lara Arruabarrena-Vecino, before storming through the second in just 22 minutes for a 7-5 6-0 victory, Angelique Kerber defeated Garbine Muguruza 6-4 7-5, Petra Kvitova advanced with a comfortable 6-2 6-3 win over fellow Czech Klara Zakopalova, Sara Errani took out Marion Bartoli 6-3 6-2, Samantha Stosur was better than Mona Barthel 4-6 6-2 6-3 and Caroline Wozniacki beat Nadia Petrova 7-6(3) 6-3 in the fourth round.
Quarterfinal pairs: Victoria Azarenka  vs. Caroline Wozniacki , Angelique Kerber  vs. Samantha Stosur , Petra Kvitova  vs. Maria Kirilenko  and Sara Errani  vs. Maria Sharapova . (photo: © Neal Trousdale)