Former world number one Ana Ivanovic made a shock first-round exit at Stuttgart's clay-court WTA tournament on Wednesday as she lost to wild-card Mona Barthel.
The 21-year-old German blasted down 11 aces to out-muscle Serbia's Ivanovic in straight sets for a 7-5, 7-6 (7/4) victory and will now face seventh-seed Marion Bartoli of France in the second round.
Ivanovic has struggled for form since she rose to world number one nearly four years ago following victory in the French Open.
Her best recent form has been at the US Open when she reached the fourth round in both 2010 and 2011.
She started her semi-final against Maria Sharapova at Indian Wells at the start of March, but was forced to retire with a hip injury.
In the day's other ties here, Russian tennis diva and world number two Maria Sharapova makes her debut against French qualifier Alize Cornet on Wednesday evening.
There will be a battle of the former world number ones later when Denmark's Caroline Wozniacki, the sixth-seed here, takes on Serbia's Jelena Jankovic for a place in the second round where the winner faces Germany's Angelique Kerber.