#3 Ander Herrera
Ander Herrera is the most important piece of Solskjaer's midfield puzzle, because of the many qualities the Spaniard brings to the table. Under Mourinho, Herrera was mostly used as a defensive midfielder, who was rarely allowed to break free into the final third. Solskjaer has transformed Herrera into the Box to Box role that he thrives in and as a result, he has gone from strength to strength under his new manager.
To say Herrera's role is as important as Pogba's might draw a lot of criticism, but the fact that the Spaniard does almost everything on the pitch is a testament to that fact. He already leads the charts, among the United players, for interceptions and tackles and he is also among the top passers in the team. This is all in a season where he has been used sporadically in the first 17 games!
But the Spaniard's most important attribute is his intelligence. He has a proper footballing brain, and he is a very good reader of the ball. His awareness of his teammates is evident as he finds the perfect option almost every time and he is always available for a pass.
The Spaniard is as involved in defense as he is in the final third and even though he does not hog a lot of limelight, Ander Herrera is perhaps the most important United player in the team right now.