"They reckon about six to eight weeks and I should be right."
With the Warriors' playoff hopes hanging by a thread with seven games remaining in the regular season and the Kiwis relying on their chief playmaker being fit for the Rugby League World Cup in November, Johnson was hesitant to specify when he expects to make a playing return.
He will spend the next fortnight trying to strengthen the muscles around his knee before having the injury re-assessed.
"I'm walking ok at the moment and don't need crutches so I'm taking it day by day but it is feeling good," he said.
"I'm not able to run for the next couple of weeks. I'll see Stew Walsh, our surgeon, in a couple of weeks and then we'll go from there."
But Kearney is confident he will make a fast recovery and hopes he will be back in the No7 jersey sooner than anticipated.
"My personal opinion is I think he'll be back a couple of weeks before then," said Kearney.
"He's moving around pretty well. I'm not a doctor or a surgeon or anything like that but I just get the feeling he could be back sooner than expected.
"He's a good rehabber and he's a pretty good athlete too so I think he'll be back a bit quicker than what we anticipate.
"Six to eight weeks, they [medical staff] said it was an ACL on Friday too, so I don't know if I'll listen to them."
Johnson is backing replacement halfback Mason Lino to slot in comfortably for Saturday's must-win clash against the North Queensland Cowboys and believes the Warriors need to focus on doing the little things right in Townsville.
"Mase is consistent. He's been really leading those (reserve grade) boys around the park and his kicking game is really solid as well.
"We really need to go up there with a mindset of grinding a game out and Mase and his calming influence and his ability to get the ball into the ingoal will certainly help us do that."
