There are reports he had a fainting spell in which he struggled to speak or move effectively, so was kept in hospital overnight and will be in the Policlinico in Milan for at least another night.
"Cassano is still not well and we need to perform further tests," confirmed Milan chief medic Rudi Tavana.
However, Cassano's agent was more reassuring, even if he released further details of what exactly happened.
"Antonio has recovered all his normal functions," Beppe Bozzo told Sky Sport Italia.
"Now he can speak normally and no longer has problems, not with his sight nor his balance."