The 18-year-old striker scored his 13th goal of the season at Brighton on Tuesday night and also provided a wonderful assist for Bruno Fernandes in United's 3-0 win at the Amex Stadium.
"We have done well over the course of the season giving him more and more exposure, more and more game time," said the United boss.
"It's not easy being a young boy – he could still play in the FA Youth Cup team.
"But he's performing off the bench or when he starts and he's developed fantastically this season.
"The sky's the limit. It's up to him. He knows what he should do, can do and must do to continue playing, but that's between us.
"Mason's way ahead of what I was at 18 or 19, that's for sure. He's got a knack of scoring goals, it's natural for him and what I could do as well.
"He's a brilliant boy to learn with and he keeps making better decisions.
"He's a centre-forward by trade but he likes to drift wide and face forwards.
"That's a different role from the role through the middle with your back to goal and linking play which Mason is improving on.
"His body is filling out and he can play that position, like we've seen with Marcus (Rashford) and Anthony (Martial) – good footballers, good goal scorers and good movement, not stuck between the posts."