Former world number one Caroline Wozniacki has withdrawn from the Internationaux de Strasbourg, less than a week before the French Open starts.
The 26-year-old Dane, the number one seed, was a set down in her first-round match against American Shelby Rogers when she retired citing back trouble.
"I felt it kind of in the middle of the first set," said the world number 12.
"At this point, I think it's important for me to try and get ready for the French Open and be 100% for that."
World number 55 Rogers, who won the opening set on a tie-break in just over an hour, will play China's Qiang Wang in the second round.