Fellaini has never truly settled at United, failing to fully win over the Red Devils fans.
But he has scored a number of key goals for the club and netted an impressive brace in United’s 4-0 win over Crystal Palace today.
And Mourinho has hailed the big Belgian, saying: “I always trusted Marouane since day one.
“I try to give him confidence and show him how useful he is for the team."
On United’s display at Old Trafford, Mourinho said: “Three points and a good performance.
"We started strong and we finished strong. We rotated. We won and that's the most important thing."
Mourinho also admits he was worried about playing Palace following United’s Champions League trip to CSKA Moscow on Wednesday.
He said: “I had concerns. Palace had one week to prepare. They lost players during the week. We had to play In Russia. I had to make changes.
“The mentality allowed me to do that. Everybody wants to play.
"I could see the difference between Mkhitaryan and Fellaini. Mkhitarayan played and Fellaini didn't in Russia.
"The momentum is good and the players are happy and confident."
United return to action after the international break but taking on old rivals Liverpool at Anfield on October 14.
