Januzaj has impressed in three outings already for the Reds this season, but his first Barclays Premier League start was a step above his past performances.
United fell behind against Sunderland after just five minutes but in the second half Januzaj hit two beautiful strikes to earn United victory.
"He's done it on the big stage now," says Carrick. "It takes a lot of things [to do that on your first start]. He's got so much ability, he's got a great attitude too. He can be anything he wants to be. He's that good, he's got that chance.
"It's just the start for him. I'm sure he's not going to get carried away with it. But his two finishes... the first was on his weaker foot, you would think. His second one was just a terrific volley. We've got a lot to thank him for."
Januzaj played with the fearlessness you expect with a young player, and Carrick revealed that he gave Adnan some half-time advice to be confident about getting into shooting positions.
"I was telling him at half-time to get in the box because there were chances for him," Carrick told Sky Sports. "It was two great finishes, so he's won us the game."