Germany's former world number one Angelique Kerber was beaten in the first round at the Bad Homburg Open grass court tournament on Monday, the last event before Wimbledon.
The 2018 Wimbledon champion has been feeling her way back since January after returning from maternity leave. The 36-year-old lost 5-7, 3-6 to Russian Diana Schneider in front of home fans.
"I made too many easy mistakes at the important moments," said Kerber "Things didn't go as I had hoped. And then it's difficult to chase on grass. She played well until the very end."
The three-time grand slam winner also crashed out in the first round on Berlin's grass last week.
Lucky loser Jule Niemeier earlier stunned top seed Maria Sakkari with a 2-6, 6-2, 7-6 (7-4) comeback victory at the Wimbledon warm-up.
Former Wimbledon quarter-finalist Niemeier prevailed after 2 hours 34 minutes when Sakkari double faulted.
The German had only made the main draw after the withdrawal of Elisabetta Cocciaretto and next faces Paula Badosa in the second round.
Elsewhere, second seed Ludmila Samsonova defeated Sara Sorribes Tormo 6-3, 6-1 and fourth seed Beatriz Haddad Maia of Brazil beat German Tamara Korpatsch in straight sets.
There were also win for Katerina Siniakova, Anna Blinkova and Linda Noskova while Caroline Wozniacki and Elina Svitolina were at one set each when their match was suspended for the day due to bad light.