Third-seeded Annika Beck topped seventh-seeded Anna-Lena Friedsam 7-6 (6), 2-6, 6-2 in an all-German quarterfinal in Nuremberg on Thursday.
That was the only match that was completed on a bizarre day interrupted by rain.
Beck will next play Dutch qualifier Kiki Bertens, who advanced when Bogota champion Irina Falconi of Italy quit with a right-ankle injury after losing the first set 6-1.
Julia Goerges advanced to her first semifinal since January when fourth-seeded Lesia Tsurenko pulled out with a left hamstring injury.
Goerges will face either Varvara Lepchenko or Mariana Duque-Marino, whose quarterfinal was postponed to Friday morning because of darkness.