The Red Devils have had a miserable campaign after seeing Ole Gunnar Solskjaer sacked while the problems have not been solved by interim coach Ralf Rangnick.
At least under the German United look much more sturdy at the back, but Maguire is still experiencing the most testing moment of his career.
There were thrashings at the hands of Liverpool, Manchester City and Watford.
And it was against the latter where the Red Devils captain had his nadir when he was sent off after two clumsy challenges within five minutes of each other.
United legend Keane has not held back when speaking about the England international and his latest comments have only sparked fury again.
“We are letting the fans down and have to come out fighting,” he said. “This team finished second last year. We’ve a bigger and better squad this year so we have to show the right attitude.
“We have big players in the team, leaders. I am sick of repeating myself, but it can’t continue like this. We need to go on a proper run, starting Monday.
“I’ve obviously seen a lot of criticism and a lot of it is absolutely correct. From what the fans and ex-players have said, we get it.”
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But Keane has slammed Maguire once again, telling fans not to bother listening to the United skipper until he starts performing.
Speaking to ITV, he said: “How many times has he said that? I wouldn’t listen too much to what Harry has to say.
“I judge a player on what he does on a football pitch, not what rubbish he comes out with about ‘we need to stick together’.
“Judge a player on what happens on a football pitch.
“United aren’t doing enough, but Aston Villa at home, you’d expect them to turn up and put in a good performance. It’s not been good enough recently.”