Emma Raducanu will take on Iga Swiatek in an intriguing quarter-final at the Porsche Tennis Grand Prix but Maria Sakkari and Karolina Pliskova were eliminated.
US Open champion Raducanu overcame Tamara Korpatsch 6-0 2-6 6-1 to set up a meeting with world number one Swiatek.
It will be the pair’s first meeting on the WTA Tour and Raducanu’s maiden encounter with a top-10 opponent.
The Briton, who is playing her first Tour-level clay-court event, won 90 per cent of points on her first serve in the opening set but that slipped to 56 per cent as she opened the door to a comeback in the second.
However, Raducanu rediscovered her composure in the decider and got over the line after an hour and 39 minutes.
Fourth seed Sakkari retired while 6-4 3-1 down to home hope Laura Siegemund, who will take on Liudmila Samsonova after she bested Pliskova 6-4 6-4.
Paula Badosa came through a third-set tie-break to beat Elena Rybakina 6-2 4-6 7-6 (7-4) and Aryna Sabalenka put a spanner in the works of Bianca Andreescu’s comeback by taking their match 6-1 3-6 6-2.
Ons Jabeur beat Daria Kasatkina and Anett Kontaveit eventually ousted Ekaterina Alexandrova in a tie-break finale after surrendering the first set.
At the Istanbul Cup, third seed Veronika Kudermetova was granted a walkover against Ana Bogdan.
Seeds Ajla Tomljanovic (6) and Sara Sorribes Tormo (7) got past Lesia Tsurenko and Varvara Gracheva respectively, while there were also wins for Yulia Putintseva and Anastasia Potapova.