PRAGUE — Slovak qualifier Rebecca Sramkova upset top-seeded Petra Kvitova 7-6 (5), 3-6, 6-4 to advance to the second round of the Prague Open on Monday.

It was another early exit for Kvitova after she was defeated by Sloane Stephens in the first round of Wimbledon, the Grand Slam she had won twice.

For Kvitova, French Open champion Barbora Krejcikova, Marketa Vondrousova and Katerina Siniakova, the hard-court tournament serves as a warmup for the Tokyo Olympics.

All the previous editions of the tournament since it became part of the WTA circuit in 2015 were played on clay.

In other first-round games, seventh-seeded Nina Stojanovic of Serbia knocked out Vitalia Diatchenko of Russia 6-7 (5), 6-1, 6-3 while ninth-seeded Greet Minnen of Belgium defeated Giulia Gatto-Monticone of Italy 6-0, 4-6, 6-1.

Former U.S. Open champion Sam Stosur of Australia recorded her sixth straight loss. She was eliminated by American Grace Min 6-3, 2-6, 6-3.

Another American, qualifier Asia Muhammad, rallied to overcome Lizette Cabrera of Australia 3-6, 6-2, 6-2 and Czech Tereza Smitkova eased past Australian Maddison Inglis 6-2, 6-2.