Very simple role (on paper), but absolutely fundamental. He was the deep-lying playmaker, often coming in between Bonucci and Chiellini to pick up the ball. This essentially made our formation a 352 in the build-up which allowed Cancelo and Spina to push higher on the pitch in possession. Allegri could have opted for Caceres instead, pushing Bonucci more in the Can role, but this would have been a lot more defensive.
This seems to be his ideal position. He is very aggressive in defense but too slow going forward, and should not be given the b2b role anymore.
So he is a terrible midfielder but a great defender? He stopped everything and then had some of the clumsiest touches and turns ever out there. Which was fine in this role cause he just passed to Bonucci, Cancelo and Pjanic.
Welcome New Barzagli, may you always play this role.