Australian Open finalist Petra Kvitova struggled with her serve and was eliminated from the St. Petersburg Open in Russia on Friday, 1 February after losing to eighth-seeded Donna Vekic 6-4, 6-1 in the quarter-finals.
The 28-year-old Czech, who rose to No. 2 in the WTA rankings by reaching her first major final since 2014 at Melbourne, 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 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 semi-finals.
Fourth-seeded Aryna Sabalenka reached the semi-finals by beating Russian qualifier Ekaterina Alexandrova 6-3, 6-4. She will next play either Kiki Bertens or Anastasia Pavlyuchenkova.
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