Top-ranked Iga Swiatek advanced to the quarterfinals of the Agel Open after Ajla Tomljanovic retired with an injury during the second set of their second-round match.
The Polish U.S. Open champion was leading 7-5, 2-2 when her Australian opponent retired due to a left knee injury at the indoor hardcourt event in the eastern Czech city of Ostrava.
Swiatek, who also won the French Open in June, will next face American qualifier Catherine McNally or Karolina Muchova.
Home favorite and two-time Wimbledon champion Petra Kvitova upset second-seeded Paula Badosa of Spain 7-6 (4), 6-4 to set up a quarterfinal against this year's Wimbledon winner Elena Rybakina, who rallied to eliminate Aliaksandra Sasnovich 6-7 (5), 6-4, 7-5.
Czech players also won the last two first-round matches on the schedule. Muchova knocked out seventh-seeded Beatriz Haddad Maia of Brazil 6-4, 6-4 and Barbora Krejcikova ousted American Shelby Rogers 6-2, 6-2 for her sixth straight victory after she won the Tallinn O
