Top seed Agnieszka Radwanska defeated Italy's Roberta Vinci 6-3, 6-2 to book her quarterfinal place at the Porsche Grand Prix on Thursday.
The Polish world no. 3 had little difficulty in wrapping up the match in 1 hour 19 minutes, and will face defending two-time defending champion Maria Sharapova or Anastasia Pavlyuchenkova in the next round. The Russian pair playing later Thursday.
Fifth seed Jelena Jankovic faces Italy's Flavia Pennetta for a quarterfinal place against Alisa Kleybanova, who upset the third-seeded Petra Kvitova on Wednesday.
Serbia's ninth-seeded Ana Ivanovic was to play German wild card Julia Goerges, with Germany's highest seed, Angelique Kerber (4), facing Carla Suarez Navarro of Spain.
Svetlana Kuznetsova of Russia was scheduled to take on second seed Simona Halep in the late match.
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