The 18-year-old goalkeeper has been the starter at the Italian giants for the last three seasons and has confirmed himself as one of the best young players in the world.
However, a contract dispute and rumours he demanded an exit over the summer soured his relationship with many of the Milan faithful.
Donnarumma eventually agreed to fresh terms but reports in Italy emerged on Tuesday saying he instructed agent Mino Raiola to try to get the extension cancelled, allowing the goalkeeper to potentially depart in January.
A report in Corriere della Sera says Raiola found a loophole in the contract which allows it to be cancelled for “moral violence”, and says that Donnarumma was subjected to unfair pressure to sign the deal.
The goalkeeper has already been paid the first three months of salary.
Duro striscione della Curva Sud contro #Donnarumma:— Simone Gambino (@SimoneGambino) December 13, 2017
"Violenza morale, 6 milioni all'anno e l'ingaggio di un fratello parassita?
Ora vattene la pazienza è finita"
#MilanVerona (foto @gumas75) pic.twitter.com/6jr4kOj6x9
The latest demands have proven to be the last straw for some Milan fans as, before the contest against Hellas Verona, they unfurled a banner which read: "Moral violence, 6 million per year and the signing of a parasite brother? Now get out, the patience is over!"
The banner refers to the keeper’s 27-year-old brother, Antonio, who also plays goalkeeper but has not featured in any games this season after joining Milan from Greek Super League side Asteras Tripolis.
The younger Donnarumma started in goal against Verona, which Milan led 2-0 at half-time. Prior to kick-off, it appeared he was spoken to by Milan captain Leonardo Bonucci.
It has been a disappointing season for Milan as, despite a summer spending spree under new owners, the club sit seventh in the Serie A table, 16 points off the pace set by rivals Inter. That lead to the recent firing of Vincenzo Montella, with his replacement the club's former midfielder Gennaro Gattuso.