You dont buy De Jong to sit back and do simple passes. De Jong is not a Busquets, Fernandinho or Carrick player. De Jong is a more Iniesta player with not as good finish and end product like Iniesta. But to find a cm player that can pass players easily and so good with the ball, there are not many out there. Then its more the wingers and strikers job to score, most of the goals. You buy De Jong to do a support role to the attacking players, like De Bruyne. But still able to score, just not as often as the attacking players.
In a 4-3-3 formation. He would play on the left or right side of the dcm player. Like this.
De Jong - Witsel/Matic - De Jong
In a 4-4-2 formation. De Jong is not the nr.6. If he does so, its just a waste of his talent, to sit back and do simple passes. He can more than that. De Jong perfect cm partnership in a 4-4-2 formation is Witsel. Witsel with his age is more composure and calmer than on this younger age. And with the young guts and energy of De Jong, he should let them flowing out, free it and play on his max. Not playing on a slower tempo as a deep laying cm doing simple passes. He should max and rise his intensity, then his dribbling will be more determination and more effective.
Sancho - Witsel nr.6 - De Jong/Pogba nr.8 - Martial.
A dream 5 men midfield to compete City 5 is.
Sancho - De Jong - Witsel - Pogba - Martial.
Those 5 are quick ball players. And all of those 5 they have high confidence and they all know they are really good with the ball. If you manage to collect and let them play together. I promise you will one of the best United football since Sir Alex time. Those 5 together. They will dominate and play really good attacking football.
Sancho - RW/Winger from Dortmund
Witsel - A nr.6, a dictate cm player for Dortmund.
De Jong - A Iniesta/De Bruyne cm player. LCM/RCM player in a 3 men midfield or a nr.8. In crisis he can play as a nr.6. You always set De Jong up to attack and help the attack, it mean he will be really close to the opponent box. Then always ready to shot outside of the box.
Sum that is how i observed and how i would use De Jong to get the best out of him and to gain the best for the team too. Coz as a LCM/RCM you get to have the ability to pass players easily, from your box to opponent box. You can pass the players easily with the ball. That is what De Jong is best on. That was what he teammates Winaldum said about him. And then is what De Bruyne good about, beside to shoot and have good passes.
And depend on the role his playing for Netherland. It can affect and you dont see his max pontential with the ball. A RCM/LCM are meant to be more a attacking role than a nr.6 or dcm role. So that is my observing and description of De Jong as a football player right now. And United and Mourinho is playing Pogba as a LCM beside Matic right now. If you buy De Jong then he will play on the right side of Matic where United have Fred and Herrera there. So that is how the whole in and out situation. If De Jong is coming, someone has to leave.