Mainoo, recalled to the starting XI by Carrick, was superb for United in victory over Manchester City last week.
And ahead of their clash with Arsenal on Sunday, Carrick said of the homespun midfielder: “Yeah, I’ve really enjoyed working with Kobbie, I think I’ve known him since he was younger.
"I think I started working with him when he was 13, 14 years old, when I was going through my badges myself. I’ve said it before: this club needs young players coming through and being the foundation, to understand what it means not just for the players or the squad, but for the club and for the supporters. It’s something we need to grasp and keep building on and Kobbie is a prime example, coming through so quickly and having a rapid rise.
"To play in some unbelievably big games and impact those games at such a young age shows an awful lot of quality, in terms of the character and to be able to handle it. Part of a career is a few ups and downs and sometimes it goes in different trajectories but we’ve seen last week what Kobbie can bring. It was great.
"He’s quite straight-faced and he doesn’t give you an awful lot but you can see the way he played, he expressed himself, he was enjoying himself. To see him like that was great.”