Udinese midfielder Assane Gnoukouri will be out for at least three months after medical tests identified a problem with his heart.
The 20-year-old only joined the club on loan from Inter last month in a bid to gain more first-team experience after playing only a bit-part role in Milan.
Gnoukouri is yet to even play a single minute for Udinese and will now have to wait for at least three months before potentially making his debut.
Udinese plan to perform the tests again at a later date, but stressed in a statement that he is to undergo no sporting activities before May.
A club statement read: "Udinese Calcio announces that the player Assane Gnoukouri did not prove suitable for cardiac problems after tests in recent days.
"The tests performed in Udine have highlighted the temporary unsuitability of the player for the next three months.
"Gnoukouri, already out of action with flu, will not be able to resume athletic activity for the period previously stated."