The Rossoneri have called a press conference for Monday to discuss the future of the 46-year-old coach, who led the club to the title in 2011
The Rossoneri raced into a 2-0 lead in Emilia-Romagna thanks to Robinho and Mario Balotelli but were left shell-shocked by Domenico Berardi's stunning four-goal salvo, with Riccardo Montolivo's late strike proving purely academic.
Milan has now called a press conference for Monday at which Allegri is expected to be officially dismissed.
"This was a very disappointing and unacceptable performance, which confirms the urgent need of a change," Berlusconi told reporters after the defeat to Sassuolo.
Allegri, meanwhile, was in a defiant frame of mind when he emerged to face the media but admitted that he could well be relieved of his duties.
"I'm ok with myself," the Livorno native hold Rai. "I have always done my best and I'll keep on doing that if I keep my job.
"Anyway, whatever happens, I'll accept it."
Milan's loss leaves the club 11th in the Serie A standings, a staggering 20 points behind third-placed Napoli.