The England international arrived at Old Trafford for £80million last month and has endured a mixed start to his life as part of Ole Gunnar Solskjaer’s side.
Although the centre back has looked impressive during his first four matches for the club United have still leaked sloppy goals and experienced the same defensive vulnerabilities as they did last season.
The 26-year-old kept a clean sheet for England during their 4-0 win against Bulgaria over the weekend and when analysing the match Keane revealed his concerns about the defender.
“I think he’s done OK,” Keane told ITV of Maguire.
“We were talking about how good he is on the ball, but defensively I still think he’s… I still have one or two question marks over him.
“I always worry about his pace on the turn, I remember the first goal against Crystal Palace where he’s not doing the basics – covering round his other centre-half.
“Listen he’s 26 years of age now, you’re worried if you’re pointing these things out to him.”
However, Arsenal favourite Ian Wright defended Maguire and justified the price which United paid to secure his services from Leicester.
“He’s a good footballer, he’s a very good footballer,” Wright said.
“He’s gone up the leagues, he’s got better. Now he’s got to Man Utd and it’s the pinnacle really.
“They’ve paid that money for him because he’s worth the money.”