Sebastien Grosjean is doubtful for his France's Davis Cup semi-final against the United States at Roland Garros next weekend.
The French number one picked up a back injury in training last week and will struggle to be ready for Friday's singles.
"For the time being, I need to talk again with the players, the staff and the doctor - even if I have an idea of my own," said France captain Guy Forget.
"Sebastien can be surprising in his ability to recover from injury, like he showed by reaching the semi-finals in Monte Carlo just after being injured in Pau."
Grosjean had his claycourt season in Spring hampered by a groin injury sustained in a previous Davis Cup match against the Czech Republic in April.
Paul-Henri Mathieu, who was the last man to beat US Open champion Pete Sampras, is the likely replacement, with Arnaud Clement certain to play singles.
"As for Paulo (Mathieu), he's ready," said Forget. "He's young, he's injury free.
"I feel he's ready and he can step in. If I call him, it's because I know he can beat Andy Roddick and James Blake."
Forget has already had to leave Nicolas Escude among the substitutes.
Escude was the hero when France pulled off a shock win in Australia to take the title last December.
But this season he has been hampered by an abdominal injury which forced him to miss the US Open.
Fabrice Santoro and Mickael Llodra are the French his doubles pair, and the draw for the tie takes place on Thursday.