SYDNEY, Jan. 11 (UPI) -- World No. 1 Caroline Wozniacki was one of three highly seeded players to lose second-round matches Tuesday at the Medibank International tournament in Sydney.
Dominika Cibulkova defeated Wozniacki, who was making her 2011 debut, 6-3, 6-3. Cibulkova saved nine of the 10 break points she faced while finishing off four of the six she forced on Wozniacki.
Flavia Pennetta pulled off nearly as big an upset by knocking off second-ranked Vera Zvonareva 7-5, 7-5. Zvonareva hurt herself with 11 double faults and landing just 46 percent of her first serves. That contributed to Pennetta piling up six service breaks.
Svetlana Kuznetsova advanced to the quarterfinals with a 3-6, 6-3, 6-4 victory over fourth-seeded and world No. 6 Samantha Stosur. Kuznetsova had to deal with only two break points in the match.
Three seeded players did manage to advance out of the second round. No. 3 Kim Clijsters raced past Barbora Zahlavova Strycova 6-1, 6-4 in 70 minutes, seventh-seeded Victoria Azarenka beat Shahar Peer 7-5, 6-3 and No. 8-seeded Li Na got by Virginie Razzano 6-4, 1-6, 6-4.
In other matches, Alisa Kleybanova defeated Maria Jose Martinez Sanchez 6-2, 6-4 and qualifier Bojana Jovanovski edged past Aravane Rezai 7-6 (7-4), 7-6 (7-4).