American Venus Williams took down top-seeded Victoria Azarenka in a second-round match Tuesday at the Pan Pacific Open.
Williams beat Azarenka by a 6-2, 6-4 margin. Azarenka, who had a first-round bye, fell to 0-3 against the seven-time Grand Slam champion.
Next up for Williams is 13th-seeded Simona Halep, who defeated Andrea Petkovic 7-6 (7-4), 6-3.
Azarenka was one of four upset victims Tuesday with No. 3 seed Sara Errani, ninth-seeded Sloane Stephens and No. 14 seed Kirsten Flipkens also losing second-round matches.
Svetlana Kuznetsova improved to 6-1 all-time against Errani with a 6-4, 6-4 decision. Eugenie Bouchard outlasted Stephens 5-7, 7-6 (9-7), 6-3 and Magdalena Rybarikova handled Flipkens 6-2, 6-3.
Second-seeded Agnieszka Radwanska cruised past Aleksandra Wozniak 7-6 (7-5), 6-0. Radwanska was last week's winner in Seoul.
Caroline Wozniacki, the No. 4 seed, discarded Flavia Pennetta 6-2, 6-3.
Other seeded players advancing Tuesday were sixth-seeded Jelena Jankovic, No. 11 seed Ana Ivanovic, No. 12 seed Samantha Stosur, 15th-seeded Sorana Cirstea and 16th-seeded Dominika Cibulkova.
Additionally, Madison Keys beat Peng Shuai 7-5, 6-2.