New United manager Louis van Gaal confirmed the former Tottenham man will be out for "a long time", though stopped short of disclosing the nature of Carrick's issue.
Van Gaal was speaking as United boss for the first time, having formally taken charge of the side on Wednesday.
Carrick has made over 350 United appearances since moving from White Hart Lane in June 2006, and played 29 Premier League games last term, an Achilles tendon injury limiting his mid-season availability.
And Van Gaal lamented the loss of Carrick's experience as he looks to make his mark on United's squad.
He said: "There is, for example, Michael Carrick. He is injured, that is in my opinion a big blow because he is an experienced player."
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