MIAMI, March 29 (UPI) -- Serena and Venus Williams won third-round matches Sunday but No. 2 seed Dinara Safina was an upset victim at the Sony Ericsson Open in Miami.
Serena Williams, the top seed, dropped Peng Shuai 7-5, 6-2 while her sister Venus eliminated Anna-Lena Groenefeld 7-5, 6-3.
Qualifier Samantha Stosur surprised Safina with an easy 6-1, 6-4 victory. Safina was one of four top 10 seeds who lost their third-round matches Sunday.
Fourth-seeded Elena Dementieva dispatched Carla Suarez Navarro 6-2, 6-2 but Li Na upended No. 6 seed Vera Zvonareva 6-4, 3-6, 6-2 and 25th-seeded Agnes Szavay dropped seventh-seeded Ana Ivanovic 6-4, 4-6, 6-1.
The eighth seed, Svetlana Kuznetsova, defeated Nicole Vaidisova 6-1, 6-4; Ekaterina Makarova upset ninth-seeded Nadia Petrova 7-5, 6-1; and the 10th seed, Agnieszka Radwanska eliminated Kaia Kanepi 6-4, 6-3.
Other third-round winners Sunday included Victoria Azarenka (11), Caroline Wozniacki (13), Zheng Jie (17) and Amelie Mauresmo.