British number one Emma Raducanu was forced to retire from her Italian Open first-round match when she was again hampered by a back injury.
Raducanu has been managing the issue in recent weeks but, after needing off-court treatment, could not continue against Canada's Bianca Andreescu.
The 19-year-old trailed 6-2 2-1 in Rome when she decided to stop.
It is the latest in a series of niggles that have dogged the US Open champion in her first full year on the WTA Tour.
"I was definitely disappointed with how today went, but I guess I wanted to give it a try," Raducanu said. "I never really knew how bad it was until I kind of went out there.
"I'm still learning when it's right to push my body and push through it, and when it's not. I guess that's something I'm learning at these tournaments.
"After Madrid, I thought that maybe taking one, two days off, it would just go away because a lot of the other small niggles I've had, they've kind of gone away after taking two days off."
Raducanu, ranked 12th in the world, will be hoping the injury improves before the French Open starts.
The clay-court Grand Slam begins on 22 May and Raducanu will be playing in the main draw for the first time.