Hart has been impressed by the start made to the campaign of his clubmate Johnson who was axed from Fabio Capello's final 23 for the World Cup.
He said: "Adam has really started the season well. He was gutted not to be involved in the summer but he has really come back firing.
"He started pre-season a lot earlier than most and he is looking really sharp.
"He really wants to make an impression in the Premier League and on the international scene."