STUTTGART, Germany — Anett Kontaveit upset fourth-ranked Sofia Kenin 7-5, 6-4 to reach the Porsche Grand Prix quarterfinals.
The 27th-ranked Kontaveit, who reached the final in the last edition of the tournament in 2019, claimed her 12th win against a top-12 opponent by beating Kenin in 94 minutes.
The American fended off nine break points until Kontaveit converted her 10th to win the first set, while errors cost Kenin the second.
Top-seeded Ashleigh Barty defeated home favorite Laura Siegemund 6-0, 7-5, and Marketa Vondrousova beat Czech compatriot Marie Bouzkova 6-1, 7-6.
Sixth-seeded Karolina Pliskova, the 2018 champion, won 7-5, 3-6, 6-3 against the 137th-ranked Tamara Korpatsch in their first-round match.
Pliskova will next face Jelena Ostapenko, who defeated Swiss qualifier Stefanie Voegele 6-4, 7-5.
Two-time champion Angelique Kerber eased past Ekaterine Gorgodze 6-2, 6-2 to book a second-round meeting against Elina Svitolina.