The 21-year old midfielder made a successful return to City's first team after more than a year out with an abdominal problem in Wednesday's 5-1 smashing of Scunthorpe United in the Carling Cup and even managed to get himself on the scoresheet.
The comeback delighted former City boss Pearce who has mentored Johnson at both international and club level.
"He's an outstanding player and it's fantastic to see him back," said Pearce.
"Psychologically, just for him to be in the first team again will be a big lift.
"I know he has the ability to go a long, long way in the game and the sky's the limit for him.
"If he gets back to the level that I know he's capable of and he is getting in City's first team, then he'll certainly be in my U-21s squad."