The Belgian international was purchased by his former Everton manager in the summer, and he has had a difficult period trying to find fitness and form.
Sky Sports quotes the midfielder saying:
What makes United different is that they stand by managers. You look at the career of Sir Alex Ferguson and he managed the club 26 years. You have to give David Moyes time as well. He is a strong character. That's why he can take the pressure. Given time he will be good for Manchester United.
Man United had the same manager for 26 years - to change that is not easy for anyone. The supporters and everybody else has to give him time.
Fellaini explained to Sky Sports the manager is "the most important person in my career. I could never say something bad about him because he has done everything for me."
He also spoke of how Moyes has disciplined him in the past, and demands certain high standards of his players. He gave an example of when he was sent off for Everton last season for violent conduct, and was subsequently punished by Moyes and made to train alone.
The player added: "I was like his son and I had been bad so I took my punishment."
Fellaini has had a difficult start to his United career, and he was not the choice of many fans last summer when it came to choosing a new face for the midfield.
However, we cannot forget what the player achieved for Everton in his time at the Merseyside club.
Last season, he scored 11 times in 31 Premier League matches, creating 40 chances along the way, per Squawka. This is a great record for a player who is not considered a creative entity.
His performances for United are also rapidly improving. He was given special praise by Manchester United's official club website writer Ben Hibbs, who recently tweeted after the team's last match:
Despite the opinions of the supporter base, Fellaini was a necessary signing at the right time.
Of course, his injuries have severely hampered his early season form, but we are now starting to see the makings of a quality midfielder. He will never have the touch and pace of more diminutive players in his position, but that is not why you purchase a player like him.
Fellaini gives Moyes options, ones he did not have before his arrival from Everton.
He has shown that he is comfortable lying deep next to Michael Carrick, but he has much more added value than that of Tom Cleverley or Darren Fletcher centrally.
Fellaini can score goals and his record proves it. United need goals from midfield and eventually the big Belgian will hope to provide them. He not only gives United aerial supremacy on set pieces and in the centre circle, but he gives them an attacking option to join the play from deep.
With Juan Mata, Adnan Januzaj and Wayne Rooney relied upon to provide the flair and grace, Fellaini can provide the power and determination. If United can capture a world-class midfielder to compliment Fellaini and Carrick in the summer, next season just might be completely different to this one.