In an interview with television broadcasters this week, Ronaldo said that there needed to be a shift in attitude within the Old Trafford dressing room in order for results to improve.
The five-time Ballon d'Or winner rejoined United from Juventus in August, having won eight major honours during his first spell at the club between 2003 and 2009, including three Premier League titles and the Champions League.
Ronaldo has returned as the oldest outfield player at Old Trafford and a senior figure within the dressing room, but also suggested that some of the squad's younger players could learn from his experience.
The issue of United's mentality was raised recently by interim manager Rangnick, who warned his players about their body language on the pitch, while former right-back Gary Neville labelled the squad "whinge-bags" last month.
Maguire, meanwhile, has seen his form suffer since impressive performances last season and during England's run to the final of the European Championship.
Ronaldo's return to the dressing room has led some to question whether he could replace Maguire as captain, having stood in for him during a 1-0 defeat to Wolves earlier this month, but Rangnick is not considering any change.
"Right now, I don’t see a reason to do that," he said ahead of United's trip to Aston Villa on Saturday.
"Harry has been the captain so far and as long as Harry is playing he will be the captain and if he’s not playing then someone else will have to be the captain. This can change from game to game just depending on who is playing."
In response to Ronaldo's comments, Rangnick said that he has not picked up on any issues regarding United's mentality, but said that he is ready to address any problems should they arise.
"In order to speak about [mentality] we need to discuss what mentality means," Rangnick said.
"As I said, so far if one of our players in the game doesn’t give his very best and put all the effort into it then I will address that, you can be assured of that.
"So far I haven't seen that but with some players they start well... we speak about Marcus Rashford for example, I think in the first 20 minutes against Villa he was good, he was on fire, he was emotionally involved.
"But then after the first 30 minutes he got worse and he didn’t play on the same kind of energetic level he did in the first half an hour.
"We need to speak about that, I do that regularly, does he need a helping hand? What does that take? So I don’t see any of the players don’t care about the club or who don’t want to perform to the best and highest possible level."
Both Ronaldo and Maguire missed Monday's win over Villa, with David de Gea skippering in their absence.
The pair will be available for selection at Villa Park after returning from hip and chest problems respectively, while Jadon Sancho and Phil Jones are also in contention to play again following their recoveries from injury.
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