Caroline Wozniacki: Top seed pulls out of Strasbourg event with back problem
Former world number one Caroline Wozniacki has withdrawn from the Internationaux de Strasbourg, less than a week before the French Open starts.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.
Defending champion and home favourite Caroline Garcia advanced to the second round by beating Jennifer Brady 6-3 6-4.
Meanwhile, Eugenie Bouchard has withdrawn from the Nuernberger Cup after injuring an ankle in training last week.
The 2014 champion said: "It's a great tournament for me with lots of great memories. I'm sorry I cannot see the fans this year and hope to be back next year."
The French Open starts on Sunday.