The last time the South Sydney star came to watch his big brother Ryan play in a decider was two years ago when Wests were beaten by Macquarie despite being hot favourite.

"I thought I might put the mock on him again if I came," Cody said. He need not have worried.

Wests were a class above Cessnock and the Rabbitohs playmaker was not surprised brother Ryan played such a dominant role to finish with three tries and man of the match honours.

"Had it not been for him wanting to work to look after his family, Ryan would have played a lot more games in the NRL," Cody said.

"As it was, he was the one who taught me about professionalism and what it takes to prepare for games. I knew he would be right up for this one so it was great to see him go so well."

Walker terrorised the Cessnock right edge defence and despite the Rosellas having a host of good performers, he was a deserved J J "Mo" Wilson Medal winner.

He crossed for two first half tries as Wests built up an 18-0 lead at the break but it was his third, just a minute into the second half, when he stepped past Scott Briggs and swotted away Blake Andrews, that ended any remote chance Cessnock had of producing a comeback.

He was replaced late in the game after getting a cut, courtesy of a stray stud, above his right eye with the four stitches a badge of honour for a job well done.

"I was a bit groggy at the end and can't remember what happened but, bloody oath, I remember the three tries and I'm not going to forget this," he said.

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Walker's dominance should come as no surprise after he scored four tries when Wests beat the Goannas 57-0 six weeks ago.

"Winning is about working hard and playing as a team and taking your opportunities and that's what we did today," he said.

"The last time we were here [in 2017 grandfinal], we were probably a little bit lethargic and complacent and that probably helped me a bit today to go as hard as I could and do everything possible for the boys."