By SABC Sport
21st March 2024
The 18-year-old was this week called up by England boss Gareth Southgate for the friendlies against Brazil and Belgium, just four months after making his first Premier League start as Erik ten Hag's side won 3-0 away to Everton.
Midfielder Mainoo has gone on to make 20 appearances this season and 44-year-old Brown, who has personal experience of coming through the youth ranks at United before going on to play for England, does not expect the youngster to get carried away by his remarkable rise.
"You can see from the way he plays that he's very calm," Brown told the media as he helped promote United's July friendly against Rangers in Edinburgh.
"I don't think he'll let all the other stuff get to him, and that's a good trait to have. He's just thinking about football, and when you first come in that's all you do think about.
"But since he's come in he's taken it upon himself to give himself the type of responsibility on the pitch that a lot of young players wouldn't usually do.
"He's been calm with the ball, and even when he comes under pressure, the way he gets out of that and passes the ball forward causes teams problems."
Brown - who made more than 300 appearances for United under Sir Alex Ferguson - is still involved at Old Trafford in an ambassadorial role and would love to see Stockport-born Mainoo make a late surge for Southgate's Euro 2024 squad.
"He's someone the club have always held in high regard," said Brown. "The way injuries have gone this season, it's possibly forced their hand to put him in, but he's also had to earn it.
"Once he's got in, he's been one of the best players in the team, if not the best. Gareth obviously sees the potential in him, and I think it's good for him that he's put in with the (England) boys to see how he reacts in training, and he might even get a game as well.
"With the confidence he has for such a young age, and the way he's playing, he's definitely earned the right to be in the squad.
"If you were looking at him right now, you would say yes (he could go to the Euros), but international football is very different.
"Hopefully Gareth sees something in him that makes him think he's worth taking a chance on. It's happened in the past with other young players and they've done really well."
Mainoo's latest eye-catching display came in Sunday's FA Cup quarter-final victory over Liverpool as United continued their upturn in form since the turn of the year.
"Sunday was one of the best games I've been at at Old Trafford and if they get another performance against Coventry in the semi-final, they could be in another final, which would be excellent," said Brown.
"In the league, other teams dropping points has given us a slight opportunity (of a top-four spot) but it will take a run of wins to keep putting the pressure on.
"The confidence coming out of Sunday will help massively. We're not the finished article but if we can go into games with that same attitude, belief and work-rate, I thin you'll see a good few more points on the board."