Davide Calabria was substituted as a precaution after feeling dizzy following a clash of heads during Milan’s 1-1 draw with FC Porto.
The incident occurred just before half-time and Calabria was seen lying on the ground just before the referee blew the whistle for the break.
The right-back did not come back out for the second half, replaced by Pierre Kalulu.
According to MilanNews.it, the reason was that Calabria had earlier clashed heads with a Porto player and felt dizzy.
He was substituted as a precaution and will undergo tests to ensure there is nothing more serious going on.
It remains to be seen if Calabria will be available for this weekend’s Serie A edition of the Derby della Madonnina against Inter.
The Rossoneri will already be without suspended Theo Hernandez, while Fode Ballo-Toure is also in doubt after missing today’s game with a bruised ankle.
Ante Rebic, Alessandro Florenzi, Mike Maignan, Junior Messias and Alessandro Plizzari are also out of action.