Pennetta, the tournament's top seed, will meet Kaia Kanepi in the quarterfinals. Kanepi advanced by dispatching Maria Elena Camerin 1-6, 6-3, 6-4.
Qualifier Nuria Llagostera Vives reached the quarterfinals of the clay court event with a 6-2, 6-0 decision over Sara Errani.
Eighth-seeded Klara Zakopalova did not have to play to reach the round of eight. Her opponent in the second round, Jelena Kostanic Tosic, had to withdraw due to a neck injury.