With Paul Robinson suspended, Carson makes his full Leeds debut just days after winning his first England U-21 cap in the 3-2 win over Holland at Hull.
Gray said in The Sun: "Old Trafford is a great place to make your first start. It’s the kind of thing you come into football for and I’m sure Scott will enjoy it.
"He’s a very confident lad and if he keeps progressing the way we think he will, he can go on to become one of the best two or three keepers in the country and play for the full England side.
"He’s agile, commands his box and is a big lad who will boss his back four. He’s had a taste of the big time as he’s been on the bench all season."
Carson is pleased the spotlight has been on Leeds’ row with Australia, who got FIFA to ban striker Mark Viduka from playing at Old Trafford for failing to turn up for their friendly in Venezuela.
Carson admitted: "It has taken the pressure off me that everyone has been talking about why Mark won’t be playing.
"Mark’s been really good this week, boosting my confidence by saying things like 'You are going to win the game for us. Go out and make a name for yourself'."
Leeds have not won at Old Trafford for 29 years but Gray is not daunted. He added: "Everyone outside our camp expects us to lose. But we don’t see it that way.
"I don’t fear them and I’m sure my players are looking forward to going there."