Pennetta took a 6-2, 6-2 decision from No. 6-seeded Tsvetana Pironkova, establishing control early by recording breaks in the first three Pironkova service games. Pennetta lost her first game serving but didn't drop another.
Seventh-seeded Polona Hercog routed No. 4-seeded Klara Zakopalova 6-1, 6-1 in a very brisk 48 minutes. Hercog, who draws Pennetta in Saturday's semifinals, won two-thirds of the points in the match. She lost only 12 points in seven service games, one of which was a break.
The other semifinal has fifth-seeded Anna Medina Garrigues going against No. 8-seeded Petra Cetkovska.
Medina Garrigues advanced with a 6-2, 1-6, 6-0 win over Irina-Camelia Begu. Medina Garrigues won 68 percent of the points in the first and third sets but lost two-thirds of them in the second.
Cetkovska came out on top of a 3-hour, 17-minute battle with third-seeded Sara Errani, winning 5-7, 6-3, 7-6 (7-4).