Pennetta, ranked No. 17, eliminated top-ranked Jelena Jankovic a day earlier. She next plays Anabel Medina Garrigues, who advanced when Victoria Azarenka retired with a shoulder injury after they split the first two sets 4-6, 6-3.
Pennetta broke Srebotnik at 5-5 with a backhand service return, then converted her first set point with an ace. She then broke Srebotnik to open the second set and again in the seventh game before sealing the win with a backhand winner.
In Friday's later quarterfinals, third-seeded Venus Williams faced Francesca Schiavone of Italy and second-seeded Ana Ivanovic of Serbia played Czech teenager Petra Kvitova.
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