Speaking on his Sky Sports podcast, Neville said Rashford must establish himself in one position if he wants to become a regular for club and country.
"He is a young player so it's not the end of the world when he comes in and out of the team and gets shifted positions," he said.
"What he does have to do very quickly in the next 12-18 months is establish himself in one position and play 100 games in that position as quickly as possible.
"He plays left, he plays right, he plays centre forward and he comes off the bench and it's difficult for him.
"He's getting great experience and there is no doubt he's had a great start to his career, but what he doesn't want to do is fall into the category of someone who continues in that mould.
"He's better than that. He really is a big talent."