Marseille have confirmed that new signing Loic Remy has a heart defect which was not identified during the striker's medical.
The problem was discovered after the France international signed a five-year contract to complete his transfer from top-flight rivals Nice.
Remy's defect did not show up in his initial medical examination and only came to light when doctors took a closer look at scans.
The 23-year-old will now not play while there are genuine concerns surrounding his health.
"More tests will be performed on Monday to give clear answers to Loic," said Marseille doctor Christophe Baudot told reporters on Friday.
"He will not play for as long as there are any doubts."
Remy, who has two international caps, cannot now make his Marseille debut at home to Lorient on Saturday.
"The news we've had since (Thursday's scans) is reassuring but we have taken this decision because the most important thing for us is not to take risks with our players' health," said president Jean-Claude Dassier.
Remy said: "It's a nuisance but the most important thing is my health.
"It's a pity that tests did not show that earlier. I'm a bit worried but not to the point I fear I might have to end my career."