Australian Open finalist Petra Kvitova struggled with her serve and was eliminated from the St. Petersburg Ladies Trophy on Friday after losing to eighth-seeded Donna Vekic 6-4, 6-1 in the quarterfinals.
The second-ranked Kvitova landed only 48 percent of her first serves, double-faulted six times and was broken five times.
Kvitova, the defending St. Petersburg champion who lost to Naomi Osaka in the Australian Open final, was playing in her 14th match in 24 days. It was Vekic’s fifth match in that time.
Vekic will next face either third-seeded Daria Kasatkina or Vera Zvonareva in the semifinals.
Fourth-seeded Aryna Sabalenka reached the semifinals by beating Russian qualifier Ekaterina Alexandrova 6-3, 6-4. She will next play either Kiki Bertens or Anastasia Pavlyuchenkova.