The City chief has continually challenged the 25-year-old England international winger to play to the best of his abilities on a more consistent basis since he drafted him in from Middlesbrough in January 2010.
There has been speculation that Mancini is due to give up on Johnson this summer and allow him to depart the Etihad Stadium for pastures new with a queue of clubs, including hometown side Sunderland, waiting in the wings.
But the Italian tactician insists that the player is very much in his thoughts and he now wants to see him step up to the plate to hold down a place in the City XI and also push back into the England set-up after missing out on Roy Hodgson's squad for Euro 2012.
"Adam is in my plans," Mancini said. "Some players think that when they don't play, it's the boss' fault. I think he has to be playing for a top club but he's got to play at his top level."
On Johnson's England disappointment, he added: "It's not my fault he didn't play in the Euros. I think for the national manager it is difficult to choose.
"Adam is a very good player and probably deserved to go. Under Capello he played regularly. But he found himself in the same situation as Micah Richards, who is also a good player.
"Sometimes players have to stay at home. Now it depends on him, not me. If he deserves to play, he will."