Lilian Thuram's proposed move to Paris Saint Germain is on hold after a routine medical detected a heart problem.
The capital club had called a press conference for Friday, where it was expected the signing of Thuram would be announced.
However, to the surprise of the press in attendance, Thuram revealed that a heart problem had scuppered his switch from Barcelona, where he had not been offered fresh terms.
"I'm holding this press conference, unfortunately it's not to announce my becoming a PSG player," said Thuram.
"But to tell you that that the doctors have detected a heart problem.
"It seems that it is the same problem that my brother had and which cost him his life on the basketball court."
The 36-year-old was completely unaware of the problem after medical tests two years ago, when he signed for Barcelona, had revealed no sign of it.
"It's a complete surprise to me," added Thuram. "I hope that everything will continue as before."
PSG coach Paul Le Guen admitted it was a big blow but did not rule out signing the former France captain in the future.
"I'm disappointed for him," he said. "It's a real shame. But we're just going to have to wait and see."
Thuram will wait until the full results of his test, which should take about a month, before deciding whether to call time on his 17-year career.