Wimbledon champion Elena Rybakina suffered an injury setback ahead of the French Open after she retired with a lower back issue in her last 16 match against Beatriz Haddad Maia at the Stuttgart Open on Thursday.
The Kazakh player won only one game in the opening set and called for a medical timeout in the second when she was 2-1 down, the women's tour said.
After play resumed, Haddad Maia won another game before Rybakina decided to retire trailing 6-1 3-1. The Brazilian will face third seed Ons Jabeur in the quarterfinals later on Friday.
Last week, Rybakina helped Kazakhstan advance to the Billie Jean King Cup finals for the second time after defeating Poland 3-1 in their qualifier.
The French Open, the second Grand Slam of the year, will be held from May 28 to June 11. Rybakina's best finish at the claycourt major came in 2021 when she reached the quarters.