Johnston, the leading try-scorer in the competition this year, hasn’t recovered from a hip flexor injury suffered in the semi final win over Cronulla.
His place will be taken by Richie Kennar, who’s played just one match this season.
“[Johnston] was never really going to be a chance to play but we gave him every opportunity. If we get the job done, he’ll be back next week,” coach Jason Demetriou said.
“We can’t afford a winger coming off the field. We made the right decision. I’m sure he’s gutted, but he is putting the team first and we move on.
“I’m really happy for Richie to get an opportunity. I think the game suits him, it’s going to be physical, and physicality is not AJ’s strength. There’s a bit of a win there.”
Demetrious confirmed Jai Arrow, who had been in doubt with a hip injury, will play.
MORE TO COME.
For a daily dose of the best of the breaking news and exclusive content from Wide World of Sports, subscribe to our newsletter by clicking here!