matuidi is a top player and willl give us a lot of energy in midfield that we lacked since pogba left. I am not sure we can play him in our current system and get the most out of him. I think a 3 man midfield will be best with Pjanic and Marchisio/Kedira but for now we will stick with the 2 man. I dont expect him to be a starter unless we change. I actually think Allegri will maybe use him for cover for Mandzukic at times just to give him mins. We all want Costa , Dybala and Bernardeschi on the field at the same time but I think allegri will want more soliditiy and Mandzukic or Matuidi will see a lot of playing time.
Anyway its good to have 4 quality Center mids again. I will always regret Vidals sale tho. It breaks my heart. We would be so good with Vidal, Pjanic, Marchisio, matuidi and Khedira fighting for spots in a 3 man CM