The $294k defender injured his right knee in the second quarter of today's one-point win over Melbourne.
There had been speculation Johnson had injured his ACL and would miss the rest of the season.
But Malthouse told the media after the game: “He seems to have hit the ground. I know there's a major abrasion on the side of his knee that's caused some discomfort but that's all I can say.
"I'm not one hundred percent sure that it's a massive injury. We're quite hopeful.”