Ole Gunnar Solskjaer insists Mason Greenwood needs time to settle amid speculation he could be in line for an England squad call-up for the European Championship.
Greenwood, 18, has scored nine goals in 26 appearances in his first full season for United and earned an England Under-21 promotion earlier in the season, attaining four caps.
England captain Harry Kane is sidelined for at least three months with a hamstring injury that required surgery and Greenwood has been suggested as a possible England squad addition for the friendlies against Denmark and Italy in March.
Theo Walcott was controversially named in Sven-Goran Eriksson's 2006 England World Cup squad, having not played a single minute for Arsenal after his winter window switch from Southampton that year. Solskjaer believes it is premature to suggest Greenwood for full honours at this stage of his development.
"I think Mason will have a top career and a long career," Solskjaer said. "Let the boy settle in now first before we talk about England and the Euros.
"Because his focus has to just be on playing more for us, improving, and when he plays well for us that'll happen by itself. I don't think Mason will have noticed. He's just been picked for the U21s, so he's focusing on his football."
Marcus Rashford is one goal shy of 20 for United and Anthony Martial has 11 this term, despite spending eight weeks out with a thigh injury. Rashford passed his season-best club tally last month and Martial needs six more to equal his career-best haul of 17 in 2015-16.
United have not had two 20-goal scorers in a single season since Javier Hernandez and Dimitar Berbatov in 2010-11 and Solskjaer is pleased with the development of the forwards.
"I don't want credit for getting more out of them," Solskjaer shrugged. "They're working hard to improve their game, they've all done well. Of course, Mason's in his first season, so to have nine goals in I don't think he's got 20 appearances yet is fantastic. Marcus is growing and improving all the time and Anthony has missed about eight weeks.
"So I'm impressed by them, they're working well, we're working on the finishing patterns. We want the consistency and I think we'll see more and more of them, because they're still very young."
