Top-seeded Kiki Bertens has overcome a slow start to beat Alison Van Uytvanck 4-6 6-3 6-3 and set up a quarterfinal against American teenager Coco Gauff at the Linz Open.
Bertens saved five of the six break points she faced to close out Thursday's win in just under two hours.
Kristina Mladenovic of France also had to come from a set down to upset fourth-seeded Donna Vekic of Croatia 3-6 6-1 6-2.
Mladenovic converted all four of her break points in the second and third sets to set up a quarterfinal with last year's Linz runner-up, Ekaterina Alexandrova of Russia.
Alexandrova beat Laura Siegemund of Germany 7-6 (7-1) 2-6 6-4.
Gauff, the 15-year-old who reached the fourth round at Wimbledon and third round at the US Open this year, advanced to her first WTA quarterfinal when Kateryna Kozlova retired during the third set of their second-round match on Wednesday.