Angelique Kerber slammed her performance during a second-round defeat in Stuttgart, where she was the defending champion and local favorite.
Kerber fell in straight sets to France's Kristina Mladenovic on Thursday. The German praised her opponent, but was not pleased with her play during the encounter.
"It was one of the worst matches I've played in months," she told reporters in Stuttgart. "It was not my day. From the beginning I was not feeling my game."
Kerber dropped to No. 2 in the rankings this week. She has not gotten beyond the quarterfinals in eight of 10 events this year.