Milan announced last week that they had been informed by Donnarumma and his agent that he would not be extending his current contract, which expires in 2018.
The goalkeeper has suffered a backlash from angry Milan fans, with fake dollar bills being thrown on the field during his appearance for Italy's under-21s against Denmark in the European Under-21 Championship on Sunday, while a banner bearing the name "Dollarumma" was held up by supporters.
However, Raiola says fans should not be angry with the player but rather with Milan for the way they failed to manage the situation.
"To start with, Gigio was convinced about staying at Milan, also because I remember when he was 14 and chose their colours after having had contact with Inter, despite his family trying to talk him out of it following their disappointment with his brother Antonio," Raiola told Gazzetta dello Sport. "Recently, though, they have been terrible.