Johnson (quad) and Gallen (ribs) will be given up until kick-off after joining the side for Friday's captain's run.

With senior players Matt Moylan (hamstring), Aaron Woods (foot) and Wade Graham (knee) already out, the duo's possible inclusion shapes as a key factor against the premiers.

Coach John Morris said Gallen could play with the aid of a painkilling injection.

"I do believe it's something they can block with a needle," Morris said.

"It's just a matter of whether he thinks it's going to be enough to take away enough of the pain. If anyone can handle it, it's Gal. He knows his body best.

"The main concern (with Johnson) is he missed four weeks with a similar injury last year. We just need to be careful."

Morris said his side, who are 2-2, would have a better idea of where they sit after Saturday's clash with the Roosters, who have established themselves as one of the competition benchmarks.

"It's a good test to see where we're at," Morris said.

"We're fairly busted at the moment, losing Woodsy last week, he joins Matt Moylan and (Wade) Graham on the sidelines.

"With that provides a great opportunity for our guys to play more minutes. We won't need any more motivation to get up for a side like the Roosters."

Morris also said fullback Josh Dugan, who copped a head knock and appeared to be hindered by back and hamstring troubles against the Eels, had been passed fit.

Rookie half Kyle Flanagan, who was a last-minute inclusion against Parramatta last week, has trained all week alongside Chad Townsend in case Johnson is scratched.

"Flanno's done most of the training with us this week," Morris said.

"He only found out he was in before kick-off last week, he knows he could be in. His preparation this week has been more than it was last week."

Australian Associated Press