The England international became the most expensive defender ever when he joined from Leicester City (opens in new tab).
But Keane is yet to be convinced that it was a worthwhile investment, after seeing the 26-year-old get caught out during his start to life at United (opens in new tab).
“I think he's done OK,” the Irishman told ITV.
“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 (opens in new tab) 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.”
Maguire has started all four of United’s Premier League games so far this season, but his new team have failed to keep a clean sheet since the opening day 4-0 win over Chelsea (opens in new tab).
FRIEND OR FOE 8 times England team-mates had major bust-ups (opens in new tab)
LISTEN FourFourTwo Podcast, Episode #14: Lads, it’s Tottenham (opens in new tab)
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Alasdair Mackenzie is a freelance journalist based in Rome, and a FourFourTwo contributor since 2015. When not pulling on the FFT shirt, he can be found at Reuters, The Times and the i. An Italophile since growing up on a diet of Football Italia on Channel 4, he now counts himself among thousands of fans sharing a passion for Ross County and Lazio.
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