While the former Everton midfielder – who much like the 20-time English champions is experiencing an upturn in fortunes – admits a return to the top four and UEFA Champions League qualification is the club's main aim this season, Fellaini knows United are well placed to kick on.
Six successive wins means United are third, eight points adrift of leaders Chelsea, and are firmly banishing the memories of a painful 2013-14, when they finished a lowly seventh.
"Last season was not good enough for Manchester United," Fellaini told The Times.
"We know that and we are working hard to put that right.
"In some ways it is too early to talk about the title because we are still building and it is only December, but we are winning matches consistently again and when that happens your belief grows.
"At the very least we have to be in the top four; we must do that. I wanted this challenge."
Fellaini endured a testing first season at United following his big-money move from Everton in September 2013, but it was a learning curve he has embraced.
He added: "It was a difficult moment because in all my career I hadn't experienced anything like it.
"I played as a professional in Belgium for two years, I played with Everton for five, I have played with the national team for a long time and it was the first time I’d faced a situation like this.
"I learnt a lot. I know the club now. I know the players. I am more confident and I am injury-free."
