Cagliari president Massimo Cellino stands by his decision to sack Massimiliano Allegri earlier this week.
Allegri was shown the door, despite Cagliari sitting comfortably in mid-table.
"I have been stupid. I should have sacked him before," Cellino told Corriere dello Sport. "Allegri profited from my good faith."
Cellino is convinced Allegri had become distracted by talk of a move to a bigger club.