That's according to former United scout Mick Brown.
Mainoo continues to be linked with a move to Serie A after a difficult season so far.
But Brown told Football Insider: “They know they made a mistake letting (Scott) McTominay leave.
“I was aghast at the fact they were even contemplating letting him go given the issues they had in midfield, and he’s done an incredible job since leaving. He’s gone away, knuckled down and become an absolute superstar for Napoli and for Scotland.
“But I think Man United have learned from the mistake of letting him go, and they’re going to take a different approach towards Kobbie Mainoo.
“There’s been a lot of talk about his future, will he stay, will he go, will the manager give him more minutes or is he going to stay on the fringes?
“As far as the club are concerned, there are no plans to let him go, because they know if he left it would be the same situation we’ve seen with McTominay. He would go and impress wherever he went, and all of a sudden everybody would be asking why he wasn’t allowed to do that at Man United.
“So if those offers do come in for him, I’d be very surprised if they allowed him to leave, and I still think he’s a huge part of their plans for the future.”
Sisamost
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Let him go on loan. He can be back next season.
wuebilmor
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you are light
Emmaveli29
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He will have the chance to prove himself ones Mbuamo goes to the afcon
vaebenopr
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If they do, then they are real Devils just as their name
zutbklnsuy
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Need to go on loan as he is quite down the pecking order & as such limited game time. As of today both Casemiro & Bruno are way ahead of him in terms of skill, quality & resoorces.
Lusdlnosy
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he should leave bcoz this useless coach Amorim will not give him playing time to get top form
Fumblmnopr
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but again. limited playing time. how can he tolerate
bukai26
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This year, since United is not playing European football, all these discussions on players not getting time are arising. For the last five-six years or maybe more than that, it has always been the other way. Utd did not have players available to play matches. So hopefully Mainoo sticks to the club this year and things will change eventually.
Heikal_Mahsir
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Agreed. A loan at best. With no option to buy.