SHENZHEN, China (AP) — Defending champion Agnieszka Radwanska lost in the quarterfinals of the Shenzhen Open on Thursday, falling to Alison Riske 6-2, 3-6, 6-0 a year after beating the American in the final.

The third-ranked Radwanska was broken three times in both the first and third sets, winning less than a third of the points on her first serve.

Third-seeded Johanna Konta fared better in her quarterfinal match against Kristyna Pliskova, withstanding 15 aces from her Czech opponent to win 6-4, 6-7 (11), 6-3.

Konta will next face another Czech player, Katerina Siniakova, a 6-3, 6-4 winner over Nina Stojanovic. The eighth-seeded Riske will play Camila Giorgi of Italy. Giorgi beat Wang Qiang 6-0, 6-2.