Fellaini was often made a scapegoat for Man United following the disastrous reign of David Moyes last season.
However, the Belgian has gone from strength to strength over the course of this campaign and was instrumental in United’s 4-2 victory over Manchester City last weekend.
Rooney praised Fellaini for the way he has bounced back following a difficult period last year.
Speaking about Fellaini, Rooney said: “He is getting used in the right way. He is a handful for defenders to mark. We like to play out from the back and if teams are pressing us then we have him as an option.
“He is probably the best in world football at bringing the ball down and getting us out of pressure and further up the pitch. He is being used in the right way by the manager and he is repaying that with goals and good performances.
“It was tough for him [last season] but he had the whole team’s support. He kept his head down, worked hard and came through that period. He is showing now what he did at Everton and why Manchester United bought him. He is a quality player. He is a different option for us. It is starting to show on the pitch.
“We knew he was working hard last season and it wasn’t just him who was struggling – a lot of us were. He was the one who took most of the blame for it. It was hard for him. Thankfully the manager has shown faith in him.”
There were jeers for Fellaini at various points last season but the 27-year-old is now one of the first names on the teamsheet at Old Trafford. Fellaini owes a lot to Louis van Gaal for his remarkable turnaround as the Dutchman seems to have brought the best out of him at the club.
A few months ago, van Gaal seemed to be using Fellaini simply as a big presence up top but some subtle tweaks in the positioning of players such as Juan Mata and Wayne Rooney has brought him to the fore. Against Chelsea this weekend, Fellaini will be hoping to continue his excellent run of form.