Fifth seed Jelena Ostapenko has crashed out of the Birmingham Classic following a surprise last-16 defeat to world No.90 Tereza Martincova.
The 2017 French Open champion suffered a 7-6 (7-4) 4-6 6-2 loss in her first career meeting with the tournament qualifier in the grass-court event in Edgbaston on Thursday.
Czech player Martincova, who also reached the quarter-finals in Nottingham last week, has been rewarded with a last-eight clash against fourth seed Daria Kasatkina, who defeated Ukrainian Marta Kostyuk 6-2 7-5.
Second seed Ons Jabeur survived a scare to scrape through with victory over Canadian teenager Leylah Fernandez.
The Tunisian was reliant on a deciding-set tiebreak to overcome her 18-year-old opponent, winning 6-4 3-6 7-6 (7-3) against the world No.66.
Russian Anastasia Potapova awaits Jabeur after she eased past France’s Kristina Mladenovic 6-3 6-3.