Defending champion Magdalena Frech was sent packing from the Guadalajara Open after a 7-5 6-4 quarterfinal defeat by 19-year-old Czech Nikola Bartunkova on Friday, while German sixth seed Tatjana Maria was knocked out by Elsa Jacquemot.
Bartunkova secured the win over Polish fourth seed Frech - who won the WTA 500 hardcourt tournament last year by beating Australia's Olivia Gadecki in straight sets in the final - in one hour and 38 minutes to advance to her first WTA semifinal.
Maria, the Queen's Club champion, was another casualty as the 38-year-old fell to Frenchwoman Jacquemot 3-6 6-4 6-4 in the quarters.
American 17-year-old Iva Jovic continued her impressive run, recovering from a second-set wobble to take out Andorra's Victoria Jimenez Kasintseva 6-3 3-6 7-6(6) in the other quarterfinal. Up next for Jovic is Bartunkova.
Canadian Marina Stakusic's run was ended by Colombian Emiliana Arango 6-2 6-3. Stakusic, 20, earlier stunned 2017 French Open champion and Latvian third seed Jelena Ostapenko in the round of 16.