The 18-year-old Belgian scored two second-half goals to help the reigning Premier League champions come from behind and seal a 2-1 win at Stadium of Light.
United midfielder Carrick was impressed by Januzaj’s impact but warned the Red Devils up-and-coming star to remain grounded despite his eye-catching start to life in the Premier League.
“You don’t want to heap too much praise on him and put pressure on him because he is so young,” Carrick told Manchester Evening News.
“He will probably have good days and he will have not so good days because he is learning the game. But at Sunderland he was top drawer. He carried on what he has been doing in training since we got back from pre-season.
“I do talk to them on the pitch but you have to trust each other. He is good enough. He may be aged 18 but he’s not a kid as a player. He is a top player. He is in the team so he is one of us. It doesn’t really matter how old you are or how many games you have played.
“The boss picked him so we trust him. There are bits of advice and bits of help that people like myself can pass on. I told him at half time at Sunderland to get in the box a bit more – so that helped, didn’t it!
“In terms of debuts, he has scored two and we have won 2-1 so what can you say about that?
“In some ways he won us the game. His performance was good. He has everything sat there for him to prosper and fulfil his potential.
“He is at the right club. He has the right players around him who are willing to help him and obviously the right manager. He has the ability. As long as he keeps along the right lines and does the right things he has got a great chance of having one of the best careers.”
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