Elena Rybakina and Tamara Zidansek were both surprise second-round losers at The Rosmalen Grass Court Championships as numerous top seeds fell on Thursday.
Third favourite Rybakina struggled to find her rhythm and fell to a 6-2 6-4 loss against world number 42 Shelby Rogers.
The American will face Kirsten Flipkens in the quarter-finals in the Netherlands after she eased past Ann Li in straight sets.
Aryna Sabalenka, the favourite at the tournament, had little difficulty in negotiating past Arianne Hartono 6-2 6-3 and she will meet Alison van Uytvanck in the next round.
The Belgian picked up the scalp of compatriot Elise Mertens, the eighth seed, with a 6-2 6-3 win over the world number 29.
Fourth seed Zidansek was another to fall as she suffered a 6-1 6-1 loss to Catherine McNally, while Veronika Kudermetova profited from Anna Blinkova retiring with the match heading for one set each.
Belinda Bencic, the second favourite, will next challenge Kudermetova after she bucked the trend of the day with a battling 7-6 (7-2) 6-4 win over Anna Kalinskaya.
Seventh seed Ekaterina Alexandrova had no trouble in advancing, meanwhile, as she saw off Anhelina Kalinina 6-4 6-2.
Maria Sakkari found herself 1-0 down against world number 109 Rebecca Marino before rain stopped play at the Nottingham Open, but the top seed responded to claim a 1-6 6-3 6-3 win.
Third seed Camila Giorgi had no such luck against Hannah Dart as she was eliminated 5-7 6-4 7-6 (7-3), while Alison Riske and Ajla Tomljanovic beat Caroline Garcia and Katie Boulter respectively in straight sets.