The 20-year-old, who made his debut for England Under-21s in a friendly against Northern Ireland last November, is rumoured to be a target for the Premier League champions.
Weir welcomed interest in the young centre-back, despite hearing nothing from Red Devils boss David Moyes, for whom he worked as a player and a coach at Everton.
"I don't know anything about it, but it is great news for our players to be linked with such big clubs," Sky Sports News quotes the 43-year-old as saying.
"Harry has a lot of attributes, for a young lad he has played a lot of games, and I would not be surprised if clubs were looking at him. But we don't want to lose him."
Maguire made his professional debut as a half-time substitute against Cardiff City in April 2011 and went on to win the man of the match award.