Redknapp said the decision of the new Manchester United manager was not really a brave one because the player is clearly "special".
He told Sky Sports: "Every now and again, and it's not very often, a player comes along and makes everybody else on the pitch - and I'm talking about top players - look average. That's what he did today.
"It was a special performance from an 18-year-old. I said before the game I didn't believe it was a risk because I've seen glimpses of this kid.
"He's special and what's the point in waiting? When you need a spark and when you need something to happen for you, which is what Manchester United needed today, go and play him and unleash him.
"He's 18 years of age and nerveless. Every time he got the ball he tried to do something with it.
"It was top class and a real pleasure to watch."
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