The Spanish shot-stopper is in line to make his debut in the pre-season game with Chicago Fire at the weekend after training with his new team-mates in the United States.
"He’s just a unique talent," Steele told MUTV in an exclusive interview. "Ultimately, I think they come around in cycles. Iker Casillas was 17 when he got in the Real Madrid team, I saw Gianluigi Buffon when he was 17 play in Scotland.
"I first watched de Gea when he was representing Spain four years ago, before I was even associated with the club and it’s just something that you tick the box and say ‘one to look at’. So my first contact was when I saw at the Euro Under-17s which Spain happened to win. He’s suited to the way that we play and the way that we want to play.
"He's got an experience that people don’t realise. He’s up to nearly 100 games and he’s not 21 until November. He’s well advanced in terms of experience but can he come and play for a club like Manchester United? The qualities we’ve all seen, and the manager has seen, have ticked the boxes. There is always an element of ‘can they handle 76,000 at Old Trafford?’ but I’ve seen him play at the Nou Camp, man of the match. Not fazed."