Neville has complete confidence in his former Everton teammate.
"We are really relaxed and we are really patient with Felli because you have seen it with players in the past like Patrice Evra and Nemanja Vidic it took them six months to settle in here," Neville told the Manchester Evening News.
"It is not just the games on a Saturday or midweek, it is the intensity of the training, the size of the club and the expectation from the fans.
"All the other things like that that go with playing for Man United it takes time to get used to. I think in the last couple of games he's played he has looked a lot fitter, he's looking more confident.
"As the games keep going on he will just get better and better."
Neville continued: "What is important for Marouane now is to play well in a match that we win and he scores a goal.
"He needs to score and win. He needs to experience that feeling when you are part of a team that wins. It is fine having that feeling as part of the squad but it is a great feeling to have it when you are in the team and win.
"That is the next step for him. He needs to start scoring from midfield. There is nobody better at that than Felli. That is the next step for him. That's what he needs to take his game onto the next step."
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