Adam Reynolds is facing a long spell on the sidelines after sustaining suspected knee ligament damage in South Sydney's 18-17 win over Canterbury.

South Sydney half-back Adam Reynolds is facing a long stint on the sidelines after sustaining suspected knee ligament damage in the Rabbitohs' heart-stopping 18-17 win over Canterbury.

In a dramatic Good Friday encounter at the Olympic stadium that was marred by violent scenes in and outside the ground, Reynolds left the ground on crutches and wearing a knee brace.

The injury occurred in the final minute of the game when James Graham caught Reynolds' standing leg as he attempted to charge down a field goal.

Reynolds slumped to the ground in agony with Graham immediately alerting officials to his plight, before becoming incensed at the decision to penalise him, then award a penalty in front of the posts that was converted by Bryson Goodwin to win the game.

The 24-year-old schemer has only missed one game since making his debut in 2012 and that was due to suspension but had a history of knee problems in his junior days.

Coach Michael Maguire admitted the injury did not look good with early diagnosis estimating a 16-week layoff which would scupper his State of Origin aspirations and place a huge dent in Souths' premiership defence.

"He's got a bit of pain in his knee, he'll have to get assessed by the doctors and see where he's at," he said.

"We'll have to see how he is in the week."

The Rabbitohs battled bravely for the two points in a repeat of last year's grand final with both Glenn Stewart and Issac Luke forced off with concussion.

Greg Inglis was also suffering with a knee problem in the first half but played the whole 80 minutes including a stint at five-eighth and also in the forwards.

"It's just an ongoing thing, it's what I have to deal with," Inglis said.

"We have really good medical staff here and they strapped it up and I was good to go."

Maguire calls on NRL to help sides with concussion

Maguire said the NRL has to find a way to help sides who lose players to concussion during a game and implement an 18th man system on the bench.

"The game has to look at having someone who can sit on the sideline and replace that player," Maguire said.

"(It doesn't matter) whether or not the opposition team lose a player but can still put 13 on the park.

"If someone comes from the field, especially for a penalty it affects us and we need to look into that and have an 18th man."

Stand-in hooker Luke Keary was outstanding for the Rabbitohs and Maguire said he was delighted with the young playmaker's performance.

"He did a good job, at time we were going side to side and the boys spoke about it at halftime," he said.

"But the boys dug deep to get the win."

AAP