Aryna Sabalenka and Caroline Garcia were each taken the distance but battled into the semi-finals at the Internationaux de Strasbourg on Thursday.
Second seed Sabalenka and fourth seed Garcia are on course for a final meeting this weekend after a pair of three-set victories.
Sabalenka came through a rollercoaster clash with Monica Puig in which she dominated the first and third sets to advance 6-1 3-6 6-2.
Meanwhile, Garcia recovered from an early deficit to defeat Marta Kostyuk 3-6 6-3 6-2 and set up a clash with fellow Frenchwoman Chloe Paquet.
Garcia had trailed the 16-year-old in the second set, too, before staging a recovery to avoid embarrassment.
Paquet dumped out Daria Gavrilova, while Sabalenka will play sixth seed Dayana Yastremska, who saw off Fiona Ferro.
At the Nuremberg Cup, top seed Yulia Putintseva and second seed Katerina Siniakova also needed three sets to reach the last four.
Putintseva will face Sorana Cirstea, while Siniakova takes on Tamara Zidansek