Nina Stojanovic was the highest seed to bow out in round two of the Prague Open on Wednesday, losing in three sets to Grace Min.
The seventh seed – ranked 90th in the world – gave former Wimbledon champion Angelique Kerber a scare on her SW19 debut at the end of last month before eventually going down 6-4 6-3.
However, despite 10 aces, the Serbian was unable to build on that momentum in the Czech capital, losing 3-6 6-1 6-4 against world number 181 Min.
Min had not won a WTA Tour main-draw match since January 2020.
Meanwhile, home favourite Katerina Siniakova – French Open doubles champion alongside Barbora Krejcikova – will resume her showdown with compatriot Tereza Smitkova on day six.
Play was suspended in the deciding set with the fifth seed leading 2-6 7-6 (7-3) 5-3.
Tereza Martincova, another of the Czechs, endured no problems, beating American qualifier Asia Muhammad 6-3 6-4.
At the Hungarian Grand Prix, top seed Yulia Putintseva was a straight-sets winner against Croatia's Ana Konjuh 6-4 6-3.
However, there was no joy for fifth seed Ana Bogdan, who was beaten 4-6 6-4 6-2 by Ukrainian Kateryna Kozlova.
At the Lausanne Open, fifth and seventh seeds Caroline Garcia and Jasmine Paolini saw off Alexandra Dulgheru and Valentini Grammatikopoulou respectively.
However, sixth seed Arantxa Rus was beaten in three sets by Russia's Kamilla Rakhimova.