#4 Midfielders do not have a well-defined role
Jose Mourinho has made more changes to his midfield than any other position. The biggest problem he is facing is that with quite decent options to choose from, he can't make the right choices as to who he should play and more importantly where.
For the most part of the season so far, no midfielder has been given a fixed position to operate from in the midfield. It has been seen that Mourinho has alternatively used Pogba, Fellaini and Matic in the deep-lying midfielder role.
This uncertainty in the position creates confusion among players as to what exactly is expected of them and they are thrown completely off their game.
With new signing Fred struggling to solidify his position in the squad Mourinho has been forced to rely on Mata, Lingard and even McTominay to provide some sort of stability to the midfield.
With no player who can organize and command the midfield efficiently, the chaos in the middle of the pitch will be their downfall.