Maria Sakkari's (28) poor form continued as the Bad Homburg Open top seed was knocked out in the first round 2-6, 6-2, 7-6(4) by lucky loser Jule Niemeier (24) on Monday.
Sakkari, ranked ninth in the world, also exited the Berlin Ladies Open in the first round last week, after ending her French Open campaign in the first round too.
He started well but struggled with Niemeier's superior first serve in the second set. Niemeier took the upper hand to go 5-3 ahead the third set and was serving for the match, but Sakkari fought back to force a tie-break.
Greece's Sakkari went toe to toe with her German opponent in the tie-break but double faults proved to be her undoing.
Former Wimbledon quarter-finalist Niemeier will face Spanish wildcard Paula Badosa in the second round.