The legendary Newcastle and England striker believes the Red Devils' starlet failed to show signs of natural goalscoring instinct in a 2-1 defeat to Spain at Wembley.
"I AM a big fan of Marcus Rashford," Shearer started in his column in TheSun.
"He gets into good positions, runs in behind defenders and is a constant threat.
"His goal at Wembley on Saturday night showcased what he is all about.
"Unfortunately his two missed chances that could have earned England a point in their Nations League match with Spain also told you where he is at right now.
"A centre-forward who is playing regularly in that position for his club probably would not have fluffed those.
"The miss from the one-on-one with David De Gea after being put through by Harry Kane was a symptom of a player not used to being in those positions in a match-day situation.
"A regular striker finds himself in those situations every week and is comfortable with them. He would put those chances away and believe in himself — you get a taste for it, it is a feeling you love.
"You look forward to it, you want it, you crave it. Even if you do miss the chance, you have the confidence to know another one will come along and then you can make amends."