STUTTGART, Germany, April 26 (UPI) -- Angelique Kerber had no trouble Thursday getting past Caroline Wozniacki and into the quarterfinals of the Porsche Tennis Grand Prix in Germany.
Kerber, who beat Wozniacki in the finals at Copenhagen earlier this year, rolled over the sixth-seeded Wozniacki 6-1, 6-2 in 63 minutes. Kerber didn't face a break point and lost just 13 points in eight service games. Wozniacki was runner-up in the tournament last year.
That put Kerber into Friday's quarterfinals against third-seeded Petra Kvitova, who was a 6-2, 6-2 winner over Francesca Schiavone in an hourlong match. She lost only 12 points when serving.
World No. 1 Victoria Azarenka moved into the quarterfinals when, after Azarenka went up 6-2, 4-4, Andrea Petkovic retired. Mona Barthel earned a shot at Azarenka with a 6-3, 6-1 decision over Marion Bartoli. She didn't see a break point in the match.
Also Thursday, fifth-seeded Samantha Stosur slipped past defending champion Julia Goerges 6-2, 2-6, 6-3 and No. 8-seeded Li Na stopped Akgul Amanmuradova 6-4, 6-4.
Li goes against fourth-seed Agnieszka Radwanska and Stosur meets second-seeded Maria Sharapova in the other matches Friday.