Bonucci says Gattuso has united the club since his appointment.
The defender said: “Now we're a machine that goes, but we still have to improve in every aspect.
“He never stops telling us every day how important the Milan shirt is and how much you should honour it every time you step on the pitch in training or in a match.
“The hits we took allowed us to improve and then Gattuso came in and was able to unite the man with the skills of every player.
“What he conveyed to me right away was what he said during his first speech, in which he made each individual feel important.
“It some games to put together all the pieces, but from that first speech it was understood that the music had changed.
“The past only counts for points in the table, we don't set limits and this team can have its say in the last three months of the season.
“I'm very attached to the theory of the precedent. My theory of the precedent says that I arrived at Juventus in the Europa League preliminaries, and we had a difficult season.
“Then the following year we all know how it went, so I put my trust in that."