Seeds Laura Siegemund and Eugenie Bouchard suffered defeats in the first round of the Luxembourg Open.
Germany's Siegemund was fancied to fare well at the indoor event, but the fifth seed succumbed to wild-card entry Francesca Schiavone in a surprisingly one-sided 6-2 6-2 loss.
Bouchard's clash looked to be going to plan as the seventh seed took the first set, but the Canadian was dumped out in a 3-6 6-3 6-3 reverse against Denisa Allertova.
There were no such woes for fourth seed Caroline Garcia, though she too was taken the distance in a 7-6 (7-2) 2-6 6-4 victory over Anett Kontaveit.
Varvara Lepchenko and Anna Karolina Schmiedlova triumphed in see-saw matches, each dominating the first set, losing the second and then rediscovering their form in the decider.
The American defeated Tsvetana Pironkova 6-1 3-6 6-1, while Schmiedlova overcame Yanina Wickmayer 6-0 1-6 6-3.
Also on Monday, Monica Niculescu beat Kirsten Flipkens 6-4 6-2.