Rugby league Immortal Andrew Johns has slammed the decision to not send Canberra Raiders forward Sia Soliola off after his brutal "cheap shot" on Melbourne's Billy Slater.

While he escaped being sent off in the 20-14 loss to Melbourne, Soliola will fight to avoid suspension at an NRL judiciary hearing at Rugby League Central on Tuesday night.

Soliola was charged with dangerous contact to the head or neck and looks set to spend a number of weeks watching from the grandstand after the incident was referred to a panel.

Winger Jordan Rapana is also set to spend at least a week on the sidelines after being charged with a grade one shoulder charge on Nelson Asofa-Solomona.

It's another blow to the Raiders who are next to no chance of playing finals football with six games remaining, with star forward Josh Papalii already serving a two-match ban for a shoulder charge.

Soliola's late swinging arm to Slater's head wasn't enough to convince referee Matt Cecchin to give him his marching orders on Saturday night and it has caused uproar among former players.

Brad Fittler has "no doubt" Soliola should have been sent for an early shower in the loss and believes he should be facing "really big penalties".

Johns says Soliola's late hit dealt a massive blow to the image of the game and it will only encourage smaller players to pursue other sports.

"It's a cheap shot, he should have been sent off. I know Sia Soliola is a lovely guy but that was a cheap shot, as cheap as they come, and should have been sent off," Johns said on Channel Nine's Sunday Footy Show.

"The ball was passed so why make the tackle? Every weekend I see halfbacks go to the line and pass and then a second or two later, a guy 20 or 30 kilos bigger than him, either smashes him from behind in the ribs or in the kidneys, or in that case he smashes him in the head with a stiff arm.

"We're not producing halfbacks in the game, how can we produce smaller guys who are creative when they pass the ball and big blokes come from behind and smash them in the kidneys or the ribs?"

Johns believes the incident is just as bad, if not worse, than Sydney Roosters halfback Mitchell Pearce's off-field indiscretion last year that resulted in an eight-game ban and a $125,000 fine.

"We're so paranoid about the image of game," Johns said.

"What about [Soliola's hit]? What about that image of the game? What about mums sitting at home watching that? What are they going to think?"

Fittler believes the fact that Slater was falling is the only thing that saved Soliola from becoming the first person to be sent off in an NRL game since David Shillington 2015.

But he says Soliola should have taken more responsibility and the fact he hit Slater so late meant "he should have been sent off without a doubt".

Players are taught to pressure playmakers but Fittler says they're walking a fine line and should be ready to face the consequences if they slip up.

"If you get it wrong it should be really big penalties. That's if you do hit them anywhere below the head as well," Fittler said.

"If your timing is out, not only should you be penalised for hitting blokes late, but you should be either sin-binned or he should be suspended."

Canberra's season has been on life support for a number of weeks and the Green Machine need to win all six of their finals games to give themselves a hope of featuring in the finals.