Defending champion Angelique Kerber will face Petra Kvitova of the Czech Republic in the Porsche Grand Prix semifinals.

The second-seeded Kerber easily overcame seventh-seeded Carla Suarez Navarro of Spain 6-2, 6-4 in Friday's quarterfinals, needing just 29 minutes to win the first set and 72 minutes overall.

The German says "I tried to be aggressive from the start, I think it worked very well."

Fifth-seeded Kvitova had a tougher task defeating third-seeded Garbine Muguruza of Spain 6-1, 3-6, 6-0.