Maguire has come in for criticism for his performances in United’s recent 1-1 draws with Middlesbrough, Burnley and Southampton.
Rangnick’s side are still stuck outside the top four places amid a poor run of form.
"I think after he came back after his injury he did extremely well, with a very good performance against West Ham," Rangnick told reporters ahead of United's Tuesday game with Brighton and Hove Albion.
"In the last two games he had some weaker moments, both against Southampton and when we conceded the goal against Burnley.
"He is our captain and I don't see any reason to change that, but he is a player who has to develop and get better, like all the other players.
"The way we play is new. In the English national team he is used to playing in a back three, here he's in a back four but not as proactive. It will take some time for him to get used to it."
Maguire has made 25 appearances in all competitions for Manchester United this season, scoring one goal.
United will replace West Ham in fourth position with victory over Brighton on Tuesday.
