#1 Marouane Fellaini
The one glaring difference between Mourinho and Solskjaer's team has been the use of Marouane Fellaini. The Belgian was an ever-present member of the Portuguese's United team. He was used in various positions in the team by Mourinho and only as a target man that Fellaini looked the most effective.
However, Fellaini's skill sets may not suit Solsklaer's style of football at Manchester United. In the speedy, flexible football embraced by Solskjaer, the static Belgian looks out of place. His lack of pace in the middle is a liability during counter attacks and as a result, the Belgian has hardly featured under the Norwegian, failing to make it to the starting eleven in the first 6 games.
He played just three minutes in the opening game against Cardiff, coming off the bench. He also came off the bench against Reading in the FA Cup, playing the last 28 minutes. In both instances, he has done nothing to impress his new manager and Fellaini looks the odd man out at United right now.