ST. PETERSBURG, Russia — 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.
DOHA, Qatar – Unseeded Elise Mertens came from a set and a break down to beat recent No. 1 Simona Halep 3-6, 6-4, 6-3 in the Qatar Open final and capture the biggest title of her career on Saturday.
Halep led 6-3, 2-0, then lost a service game for a third time to see the second set back on serve. Mertens continued to pressure, missing two more break chances in the seventh game but finally breaking – to love – in the ninth. The set was the first Mertens took from Halep in three matchups.
Mertens broke again to start the third set, Halep leveled at 2-2, but Mertens finished stronger and won her fifth career title.
The Belgian beat two other top-10 players this week, Kiki Bertens and Angelique Kerber.
Halep’s first final appearance since August guaranteed she will rise one spot to No. 2 in the rankings on Monday.
BUENOS AIRES, Argentina — Top-seeded defending champion Dominic Thiem of Austria advanced to the Argentina Open quarterfinals Thursday, beating Germany’s Maximilian Marterer 6-4, 6-4.
Thiem will face Uruguay’s Pablo Cuevas, a 6-4, 7-5 winner over Portugal’s Joao Sousa.
Fourth-seeded Diego Schwartzman of Argentina beat Slovenia’s Aljaz Bedene 6-4, 2-6, 6-2 to set up a match against Spain’s Albert Ramos-Vinolas. Ramos-Vinolas beat compatriot David Ferrer 3-6, 7-6 (9), 6-3.
Ferrer promised to retire in May at the Madrid Open. The participation in the Buenos Aires tournament is one of the last of the 36-year-old’s career.