The 29-year-old has and will continue to undergo tests in a Milan clinic, but the Rossoneri are confident that the player is doing well.
"I spoke to Cassano five minutes ago and he was in a good mood," Vice-President Adriano Galliani told Sky Sport Italia. "He seems calm.
"Cassano is strong and will certainly recover. The whole squad is supporting him."
Galliani, though, refused to go into too much detail regarding what has actually happened to the former Sampdoria player.
"Every patient has a right to privacy and this is the case for Antonio too," Galliani continued in the interview.
"There are doctors there and they are looking after him. I can't give a diagnosis.
"I don't know how long it will take for him to return. I'm not a medic, that is not my profession. He's being looked after."