Man United have yet to find their balance since the arrival of Alexis Sanchez. They have changed their formation from 4-3-3 to 4-2-3-1 to accommodate Sanchez thus making Pogba ineffective in the middle.
To much players cutting inside such as Martial, Sanchez, Lingard making Pogba seem inefficient.
When Matic is the only person in the middle to cover the defense, the wing back are not permitted to push up making the opponent easier to stay compact.
Mourinho now has the dilemma whether to play Sanchez in the midfield trio or dropping Pogba or kept playing both but choking their own midfield.
I do believe Sanchez could play 4-3-3 alongside Lukaku and Martial/ Rashford but need another creativity in midfield other than Pogba. Play Mata instead of Lingard. Play Herrera, he is not gifted as Mata but he is a busy bee and can keep the ball flowing forward.
To win, i do believe they need to do this:
i) keep the pass simple and push the ball forward faster.
ii) push the wing back to stretch the opponent.
iii) start passing to the channel instead of diagonal pass.
Hope they still can push to catch Man City.