The winger could make his debut in Saturday's Premier League opener against Leeds United.
"I think he's been linked with us for a couple of seasons now and it felt a bit like my transfer when I was joining Manchester United, where it didn't happen one season but the following season we managed to get it over the line," Maguire told Sky Sports.
"I'm really excited for him, he's an exceptional talent.
"He's the type of player - with the confidence he has - who can be a real star for this club and I feel like in the future and the success we have, he can have a big part to play."
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