Home supporters called for Ferrara's sacking well before the final whistle as Juve were trounced.
Italy defender Chiellini insists it is the players, not Ferrara, who must take responsibility for their recent dismal run.
"The problem is not the coach," said Chiellini. "We always let in stupid goals. The coach cannot prepare for that!
"With all due respect to Milan, we conceded three goals from dead-ball situations. It was avoidable, if only we had paid more attention."