STUTTGART, Germany — Top-ranked Naomi Osaka withdrew from the Porsche Grand Prix semifinals because of an abdominal injury on Saturday.

Osaka said she began to feel the injury before her quarterfinal on Friday, when she came back from 5-1 down in the third set to beat Donna Vekic of Croatia.

"I wanted to wait to see if I could play. I woke up today and I had to roll out of bed, then I decided I wasn't able to play," Osaka said.

Her opponent, No. 8-seeded Anett Kontaveit, received a walkover into her fifth WTA final. Kontaveit also advanced to the quarterfinals when Victoria Azarenka retired hurt in their third set.

Osaka didn't believe her abdominal strain would slow her down too long, as she said she's endured many of them.

Kontaveit will play Petra Kvitova in the final, after the Czech beat Kiki Bertens of the Netherlands 7-6 (3), 3-6, 6-1 in two hours.

The third-ranked Kvitova has reached her fourth final of the year, and aims for her second title, after winning Sydney in January.

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