Angelique Kerber has withdrawn from the grass-court event in Birmingham, England, with an ongoing hamstring problem.
The world No. 1 experienced the injury in Madrid, and has not won a match since then. She said the problem recurred when she began training again following the French Open. She is also scheduled to play next week in Eastbourne, but indicated that no decision has been made about competing there.
"It was fine but then it comes back a little bit," she said. "I'm still hopeful of playing next week at Eastbourne, and I really want to be right for Wimbledon."
Kerber was the defending champion in Birmingham.