Mancini is cracking the whip as he believes Johnson "has everthing to become one of the top wingers."
Johnson scored once and set up another goal for Samir Nasri as City changed their side completely from the 6-1 win over Manchester United and still won 5-2 at Wolverhampton Wanderers to reach the quarter-finals of the Carling Cup.
But Mancini was still not totally satisfied with the performance of the former Middlesbrough player.
played well
He said: "Sometimes he thinks: `Okay in this game I scored one goal, I did an assist, that is enough'. I think Adam, because he is young, can improve a lot. He needs to think in a different way.
"He needs to think: `I scored one goal, I did one assist, I should continue because I want to score another goal and another assist, and run back to defend'.
"He can do this if he wants. My opinion is this, he has everything to become one of the top wingers."
Mancini added: "Adam is young, he is in his third season in the Premier League. I am disappointed when he doesn't put everything on the pitch.
"He played well, but for the second goal Wolves scored (by Jamie O'Hara), he never followed his opponent. Adam is the only one winger we have in the team."
