The top-seeded Italian produced a dominant display to brush aside newcomer Stephens 6-1, 6-1.
Pennetta, who has given up only four games in the first two rounds of the WTA clay-court tournament, will face veteran Jill Craybas next, after the American defeated Anna-Lena Groenefeld of Germany 3-6, 6-0, 6-4.
Story continues below ↓advertisement | your ad hereAlso advancing was second-seeded Aravane Rezai. The Frenchwoman beat Renata Voracova of the Czech Republic 6-4, 6-2 on center court.
It was the second time the pair have faced off, and like in their first match, Rezai comfortably beat the player ranked more than 60 places below her.
Rezai is likely to face more of a test in the quarterfinals when she plays fifth-seeded Arantxa Parra Santonja, who beat fellow Spaniard Nuria Llagostera Vives 6-4, 6-3.
Also, Lucie Safarova of the Czech Republic had to come from behind to beat Karolina Sprem of Croatia 2-6, 7-5, 6-3. It was a hard-fought victory for third-seeded Safarova, who rallied at the end of the second set to save the match, before winning the third.
Barbora Zahlavova Strycova of the Czech Republic won the final match of the day against Akgul Amanmuradova of Uzbekistan, 3-6, 6-4, 6-0.
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