Donnarumma's agent Mino Raiola is launching legal action against the club to have his contract terminated.
Before the tie, Donnarumma’s name was jeered loudly when read out by the speaker and there were insulting chants aimed at him throughout the warm-up.
A group also lifted up a banner: ‘Moral violence, €6m per year and the signing of a parasite brother? Now go, our patience is finished!’
They were referring to the fact Milan brought in his brother Antonio – who is on the bench tonight – as one of the keys to keeping him at the club.
Footage also emerged before kick-off of captain Leonardo Bonucci trying to console a weeping Donnarumma in the locker room.