The 2007 Norm Smith medallist suffered a wrenched left knee during the third quarter of Geelong's preliminary final win over West Coast.
The club confirmed on Sunday that the knee is clinically stable despite significant swelling, and the 28-year-old will use a hyperbaric chamber through the week in a bid to prove his fitness.
The Cats will give Johnson until Saturday morning to prove his fitness, Geelong midfielder James Kelly said.
"It is Steve Johnson, and he's been playing on one leg for his whole career," Kelly said.
"You're not really sure what he's capable of. I think if there's any question mark they'll probably say 'no', but at the end of the day that's up to Steve and the coaches."
Johnson was carried from the field on a stretcher, although he later returned from the rooms and walked around the boundary, which drew a big cheer from the Geelong faithful.
"I had a look up [at the replay] as they were taking him off the ground, and it looked pretty bad," Kelly said.
"To see him walking out was a great sign for us. Hopefully he can get up. It would be fantastic."
One of the big positives to come out of the Cats' win over the Eagles was the successful return of veteran midfielder Joel Corey, who had been sidelined by a groin injury since mid-August.
"He (Corey) was probably a little bit rusty yesterday, given the footy he's missed, but knowing the guy that 'Smithy' is, he'll be much better for the run," Kelly said.
"He'll play his hardest next week. He's really strong around the stoppages, and that's something that you need in a Grand Final, which will probably end up being a fairly contested sort of game."
The battle in the middle is expected to have a big impact on the result, and Kelly is excited about the prospect of taking on a gun Magpies midfield boasting Dane Swan, Scott Pendlebury and Dale Thomas.
"I think both midfields are pretty strong," Kelly said.
"These days, a lot of the game is played in the midfield, and those battles are going to be huge.
"We'll be ready for them, and I'm sure they will, too."
Kelly was full of praise of the role key forward Tom Hawkins has played in Geelong's surge to the Grand Final.
Hawkins was outstanding when the Cats beat the Hawks in week one of the finals, and he made another solid contribution against the Eagles.
"He was a bit up and down during the year, but his last month has been fantastic," Kelly said.
"He's a big, strong guy and he's playing that way.
"Yesterday he didn't mark too many balls, but he just made a contest every time, [while playing] on a good player in Darren Glass.
