Sydney Roosters halfback Cooper Cronk admits he is a "long shot" to play in Sunday's NRL grand final against Melbourne due to a shoulder injury.

Scans confirmed the 34-year-old had suffered "severe" damage to his rotator cuff in the Roosters' preliminary final win over South Sydney on Saturday.

Cronk said on Monday that he would do everything he could to be fit enough to face his former teammates.

"It's still there, when I woke up this morning it was still attached, which was a good thing." Cronk joked with reporters.

Cronk had his arm in a sling at the Roosters media day, saying that he needed to let the injury settle before testing his capabilities.

"I can move it. The best thing to do is just immobilise it … I need to let it rest, need to let it recover then see where it is in a few days time," he said.

"I don't know what my realistic chances are, but I'm a long shot, that's not lying."

Cooper Cronk suffered the injury at the end of the first half of the preliminary final victory over Souths. ( AAP: Dan Himbrechts )

Cronk refused to be drawn on the full extent of his injury, saying only that he would do everything he could to be ready to play.

"I'm not going to go into the details of the injury, at the moment, with all due respect it is on a need to know basis, and at the moment, you do not need to know."

"At some stage God or science will say, but until then I will do everything I possibly can."

When asked whether he expected to be targeted by the Storm in defence if he played, Cronk noted that it would not be any different to a normal game.

"I think I'm a spot every week.

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"If I'm there with my boots on and this Roosters jersey on, then anyone can run at me."

Should Cronk be ruled out, either Ryan Matterson or Sean O'Sullivan will likely play alongside Luke Keary in the halves in what will be the biggest game of their careers.

Matterson would be the more likely choice after he replaced an injured Keary just last month, but he has only played eight games at five-eighth and one at halfback in his three-year NRL career.

The 23-year-old — who played under-20s in the halves for NSW — will join Wests Tigers next year after acting as a utility for the Roosters this season.

Another option could be 20-year-old O'Sullivan, who debuted as a teenager against the Gold Coast in July.

The Brisbane-bound son of former Roosters recruitment manager Peter O'Sullivan has played three other games off the bench this year and could return there on Sunday if Matterson is named in the starting line-up.

Coach Trent Robinson also has former Canberra playmaker Mitch Cornish as an option, however he hasn't been seen in first grade since round one when he replaced Keary.

Cooper Cronk and Billy Slater were teammates at the Storm for fourteen seasons. ( AAP: Julian Smith )

Cronk's former teammate Billy Slater is also at risk of missing out on the premiership decider, although his involvement will depend on the NRL judiciary rather than the healing process Cronk is facing.

The pair played at the Storm together for 14 seasons, winning two premierships together, and Cronk admitted that his friendship with Slater meant he was conflicted as to whether Slater should be banned.

"I knew that question was coming up," Cronk said.

"There are two sides of it for me, well three sides. One is I'm a really good mate; one, I'm in the opposition this week; and three there is respect to the judiciary as well.

"I've got a different answer for all three of them, and I'm not going to say that publicly, so you're going to have to work out which one is which."

AAP/ABC