Seventh-seeded Paola Badosa of Spain has upset tournament No.4 Kristina Mladenovic 7-5 6-7 (7-5) 6-2 in an error-strewn match to reach the Lyon Open semi-finals.
Neither player looked comfortable on serve, combining for 21 double faults and 15 service breaks at the indoor tournament on Friday.
Badosa next faces 18-year-old Clara Tauson of Denmark, who continued her fine form by beating Camila Giorgi of Italy 6-3 6-1.
Tauson had six aces and did not face a break point, also breaking Giorgi’s serve five times in a dominant display.
The 139th-ranked Tauson, a former Australian Open junior champion, knocked out top-seeded Ekaterina Alexandrova in the first round.
She and Badosa are both looking to win their first WTA titles.
Second-seeded Fiona Ferro joined them in the last four in her bid for a third career title.
Ferro rallied to beat unseeded 19-year-old Clara Burel 2-6 6-1 6-3 in an all-French match where they dropped serve 12 times between them.
She next plays play Swiss player Viktorija Golubic, who beat unseeded Belgian player Greet Minnen 6-3 7-6 (7-0).
Golubic, a qualifier ranked 130th, is seeking her second career title.