Daria Gavrilova crashed out of the Grand Prix De SAR La Princesse Lalla Meryem in the quarter-finals, while top seed Anastasia Pavlyuchenkova needed three sets to see off Lauren Davis.
Third seed and world number 26 Gavrilova suffered a 7-6 (7-5) 6-4 defeat to Sara Errani, the Italian's prowess at the net coming to the fore as she claimed eight breaks of serve to the Australian's seven.
Pavlyuchenkova, meanwhile, survived a second-set blip to beat Davis 6-4 3-6 6-3 and set up a semi-final with Errani. The other semi will see Francesca Schiavone face Varvara Lepchenko after they overcame Tatjana Maria and CiCi Bellis respectively.
At the Prague Open third seed Barbora Strycova claimed a three-set win over eighth seed Katerina Siniakova 6-3 5-7 6-3 and takes on Mona Barthel next, the German needing two tie-breaks to see off Camila Giorgi.
Kristyna Pliskova ended qualifier Beatriz Haddad Maia's run to reach the last four, coming from behind to win 6-7 (5-7) 6-4 6-2. She will have to wait to learn her semi-final opponent, with Ana Konjuh and Jelena Ostapenko's match suspended due to darkness at 1-1 in the decisive set.