Frenchman Richard Gasquet said a painful nerve injury in his thigh caused him to retire from his French Open third-round match against compatriot Gael Monfils midway through the third set on Sunday.
Monfils advanced to the fourth round with a 7-6(5) 5-7 4-3 win, and will now face third seed Stan Wawrinka of Switzerland.
"Nothing's ever written in stone," a disappointed Gasquet told reporters at Roland Garros. "I had had back problems for the past two, three weeks with a kind of neuralgia in the leg. No sensation in the thigh. Very painful, but my back is better.
"I did my best for this neuralgia to disappear. I think the nerve is probably still a bit irritated. I tried as much as I could but towards the middle of the second set I understood it was going to be very hard.
"So disappointed, of course. My back doesn't hurt so much, but I simply couldn't go on any longer."
Gasquet said he would have a scan to assess the problem and denied that his decision to pull out of the match had anything to do with his friendship with Monfils.
"Gael or anyone else, it would have been the same thing. It's a tennis match. It's just that I couldn't play. Of course he's a friend but I couldn't play. I had reached the end of my tether. It was too painful to go on," he added.
"I'm going to get an MRI. My back's better. I think it's not as serious as what it was before but this area there is affected and I really can't push my thigh anymore."
(Reporting by Simon Jennings in Bengaluru; Editing by Clare Fallon)