The centre-back faces an uncertain future at the Red Devils as he continues to struggle with life at Old Trafford.
It was revealed last week that he is set to lose the captaincy ahead of the new campaign, with Bruno Fernandes set to take over.
talkSPORT understands that West Ham boss David Moyes is a big fan of Maguire, with a summer move potentially on the cards.
His status as a consistent feature in the United back line is diminishing, and has now revealed that he is no longer captain.
In a statement on Twitter he said: "After discussions with the manager today he has informed me he is changing captain. He outlined his reasons to me and whilst I'm personally extremely disappointed, I will continue to give my all every time I wear the shirt.
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"So I wanted to say a massive thank you to the Manchester United fans for all their brilliant support whilst I've been wearing the armband.
"Since the day I took on the role, three and half years ago, it's been a huge privilege to lead Manchester United and one of the proudest moments of my career to date.
"It's one of the greatest honours in club football. I've done everything I possibly could to help United be successful - on and off the field.
"I will always be grateful to Ole Gunnar Solskjaer for first giving me the responsibility and I wish whoever now takes it on every success and they will have my full support. Harry."
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Despite an uncertain future, Maguire has been hard at work during the summer ahead of the new season.
He was spotted training with Chelsea legend and three-time Premier League winner Ricardo Carvalho.
Should he leave United in the transfer window, he would depart with 175 appearances to his name in all competitions.
He has scored seven goals for them since his 2019 move from Leicester, which saw his £80million switch make him the most expensive defender ever.
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