Pennetta rolled by Sloane Stephens 6-1, 6-1, piling up five breaks in Stephens' six service games. Pennetta lost only four points on serve in the first set and 10 in the second, despite having her serve broken once.
Second-seeded Aravane Rezai had five service breaks in a 6-4, 6-2 win over Renata Voracova but No. 3-seeded Lucie Safarova and fourth-seeded Gisela Dulko each needed three sets to advance.
Safarova fought through a tough 2-6, 7-5, 6-3, victory over Karolina Sprem that took nearly 2 1/2 hours. Dulko was shaky in the second set but came away with a 6-2, 1-6, 7-6 (7-1) win over Tatjana Malek.
Fifth-seeded Arantxa Parra Santonja stopped Nuria Llagostera Vives 6-4, 6-3 and No. 8-seeded Barbora Zahlavova Strycova rallied for a 3-6, 6-4, 6-0 win over Akgul Amanmuradova.
Also, Jill Craybas defeated Anna-Lena Groenefeld 3-6, 6-0, 6-4 and Ana Vrljic slipped past Arantxa Rus 7-5, 5-7, 6-4 in a match that saw 17 service breaks in 34 games.
Copyright 2010 United Press International.