Sydney Roosters officials were warned their grand final gamble on Cooper Cronk could have backfired as badly as was the case with  Graeme Langlands in 1975 and that he could not be replaced after the line-up was announced. For them, that risk was worth it.    

As revealed by Roosters doctor Ameer Ibrahim after Sunday night's stunning 21-6 defeat of Melbourne, Cronk did not receive a pain-killing injection for his broken shoulder until 6.45pm as it was estimated the dose would wear off within 80 minutes.

Therefore, the needling couldn't be done any earlier if he was to get through to halftime but NRL rules require teams to be finalised 60 minutes before kick-off and the Roosters had submitted their line-up at 6.22pm. Changes are only allowed if a player suffers an injury in the warm-up.

It is understood the Storm were asked if they would let the Roosters replace Cronk if the injections – two doses of local anaesthetic - didn't work and he was unable to play but the rules do not permit teams to call up a late replacement for a player ruled out with a pre-existing injury.

As a result, the Roosters would have been reduced to 16 players for the Telstra Premiership decider – although it could be argued they only had 12 players on the field as Cronk was a virtual passenger, like Langlands when he famously wore white boots in St George's 38-0 thrashing at the hands of Easts 43 years earlier.

Former Roosters doctor John Orchard said Ibrahim and the club's medical staff deserved credit for getting Cronk on the field, tweeting: "Hard for those who haven't been there to appreciate pressure on medical staff in Grand Finals, with millions watching.

"You go back to 1975 where a needle numbed a nerve in Langlands' groin and he couldn't kick – that can be the outcome if medical staff get it wrong. Not an easy job in these situations".

Besides the injections which enabled Cronk to play, Roosters head physiotherapist Steph Brennan worked up to 10 hours per day on the star halfback since he sustained the injury in the previous Saturday night's preliminary final win over South Sydney.

Other players to have recently suffered a fractured scapula include Wests Tigers five-eighth Josh Reynolds, who returned after five weeks on the sideline but only lasted four matches before requiring season-ending surgery, and Newcastle prop Jacob Saifiti, who missed 14 rounds.

So vital was Cronk considered to the Roosters premiership hopes that no stone was left unturned in a bid to enable him to play, including the use of hyperbaric chambers, cold laser treatment, infra-red saunas, a bone stimulating machine and designing a hard plastic splint for his shoulder blade.

"Somehow, he had the mental strength to block out the pain but also to lift the other players around him," Ibrahim said. "It was astonishing."

With the aid of the injections, which included a third dose of local anaesthetic at halftime, Cronk was able to direct the Roosters around until the 78th minute like an on-field coach, but his actual involvement was minimal and included no runs with the ball.

"Cooper is never a risk and we were ready for if it didn't work out," Roosters coach Trent Robinson said.

However, few can say confidently that the Roosters would have won if Cronk had not played. He was constantly organising teammates in attack, while playing a game of hide-and-seek in defence when the Storm forwards attempted to target him.

"His presence was underestimated," Clive Churchill Medal winner Luke Keary said. "It is hard to explain how he makes you feel on the field and what he does to a team's performance."

If there was any doubt that Cronk has a future in coaching after he retires, his grand final performance was the perfect audition and Robinson said he had already had a huge impact since joining the Roosters from the Storm this season.  

"That's just made us all improve as coaches and players, we have seen how it is done and we have all improved because of that," Robinson said.

"Coaching is very different to what it was a long time ago. Coaching is about developing players to coach other players, it’s about a big team performance and that is what has happened."