The 17-year-old Czech's first career semifinal will come against Nadia Podoroska, who rallied for a 1-6, 6-4, 6-2 victory over Canada's Eugenie Bouchard. The Argentine had a 4-0 edge in aces over Bouchard.

Katie Swan of Great Britain also reached her first career semifinal by beating Japan's Nao Hibino 6-3, 3-6, 6-3. Swan will face third-seeded Magda Linette after the Polish player beat Canadian seventh seed Rebecca Marino 7-6 (10), 6-3.

Zavarovalnica Sava Portoroz

Romania's Ana Bogdan saved seven of 10 break points while stunning second-seeded Beatriz Haddad Maia of Brazil 6-1, 1-6, 7-5 to reach the semifinals in Slovenia.

Bogdan moves on to face third-seeded Elena Rybakina. The Wimbledon champion from Kazakhstan advanced in a walkover when Ukraine's Lesia Tsurenko withdrew prior to the match.

Anna-Lena Friedsam, who upset top-seeded Brit Emma Raducanu on Thursday, notched a 1-6, 7-6 (4), 6-3 victory over France's Diane Perry. The other quarterfinal between Czech Katerina Siniakova and Italy's Jasmine Paolini was postponed until Saturday.