Cronk injured his left shoulder as he took a field goal attempt on the stroke of halftime on Saturday night and was little more than a passenger during the second half.

In front of a record crowd of 44,380 in the final game at Allianz Stadium before it's redeveloped, the minor premiers won through to their second grand final in six years.

Former Queensland and Australian playmaker Cronk was brought to Bondi Junction to deliver the premiership that Mitchell Pearce couldn't and now he's in doubt to face his former club Melbourne in the season decider.

Cronk was injured after being crunched by Adam Reynolds as he attempted to break a 4-4 deadlock and got up clutching his left shoulder.

After the Roosters physios worked on him at halftime, he was visibly hobbled after coming back out and could barely raise his arm.

At times he could only put his body in front of opposition ball carriers, hoping his teammates got there to help out.

In the end, the Roosters' goalline defence proved the difference, with Souths enjoying 30 tackles inside the opposition red zone but unable to cross for a try.

The Roosters went ahead 8-4 when Joseph Manu, despite the attention of Greg Inglis and Alex Johnston, popped a beautiful pass in traffic to send Blake Ferguson over.

The Rabbitohs were clearly targeting Cronk, with Junior Tatola smashing him after he had passed the ball.

However, Sio Siua Taukeiaho couldn't convert the two points from the resulting penalty.

From the next set the Roosters iced the game after centre Paul Momirovski, who was a surprise late inclusion for the suspended Latrell Mitchell, crossed for the decisive try.

When Luke Keary lofted a bomb, Campbell Graham failed to reel it in and Momirovski, who was playing the second game of his career, pounced.

The Roosters will receive a big boost going into the grand final, with Mitchell and prop Dylan Napa to return.

Roosters skipper Jake Friend will come under the attention of the match review committee for a tipping tackle on Greg Inglis in the first half.

Cronk will have scans on his shoulder. When coach Trent Robinson was asked if his No.7 would be fit in eight days time, he said: "I'd say he'd be right to play next week.

"(Taking Cronk off at halftime) wasn't even discussed. To be honest, I didn't even ask how he was.

"Cooper knows how he is. He needed to get work done at halftime and he was always going to go back out there."

Rabbitohs coach Anthony Seibold denied his side had missed an opportunity to target Cronk.

"We didn't necessarily think to chase him," Seibold said.

"We tried to put him under pressure when he kicked the footy. That didn't have any impact on the game.

"You can spend your life targeting Cooper. I don't understand. He was still making his tackles."

Australian Associated Press