Strasbourg - Top-seeded American Madison Keys withdrew from the Strasbourg International on Thursday because of an elbow injury, giving French player Kristina Mladenovic a walkover into the semi-finals.
Keys, who rallied from one set and 5-0 down to beat Mirjana Lucic-Baroni 4-6, 7-6 (3), 7-6 (0) on Wednesday, pulled out as a precautionary measure ahead of the French Open, which starts on Sunday.
Mladenovic will next face countrywoman Virgine Razzano, after she rallied to beat Elena Vesnina of Russia 4-6, 6-1, 6-1.
Elsewhere, American Sloane Stephens reached the last four after second-seeded Jelena Jankovic of Serbia retired from the match after losing the first set 6-1.
Stephens next faces No. 3 Samantha Stosur of Australia, who took two hours to beat Croatia's Ajla Tomljanovic 6-4, 3-6, 6-4.