Penrith No.9s have always made a point of being the difference in Panthers' grand final wins.
Think Royce Simmons in 1991, who scored two tries in his departing game against Canberra and was unlucky not to win the Clive Churchill Medal.
Or Luke Priddis in 2003, the Penrith hooker who scored one try and set up their other two to rightly earn him the top individual prize.
And in 2020, Api Koroisau will be just as important at dummy-half.
Just like in 2003, Sunday is expected to be wet.
It's likely to leave it as a battle in the middle, where options and good service are also everything out of dummy-half.
"He's a fantastic player," Simmons said.
"I remember early in the year he said I might come talk to you Royce, pick a few things up.
"I thought no, I don't need to mess you up. Keep playing the way you're playing.
"He's a good player, he's very good at taking the markers out of the game and running the ball when it needs to be run.
"He takes a lot of pressure off his ball players and kickers, because they are worried about him first."
Koroisau is just the man Penrith need for the job.
The 27-year-old was Penrith's best in last week's win over South Sydney, and has helped change the way the Panthers attack in 2020.
He's been sound defensively, as Ivan Cleary pointed out this week with his different style to most others in the team.
The hooker has in turn arguably been the buy of the year, with Penrith's fate potentially swinging on a last-minute decision to head to the Panthers over Canterbury.
"He's certainly one of them," Simmons said.
"I am probably a bit bias, but I think so.
"But at the end of the day he won't care about buy of the year. He wants to win this grand final.
"There is no trophy for buy of the year, but a big reward for winning a premiership."
The job Penrith do on Koroisau's opposite number will be just as match-defining.
Last week they contained Damien Cook perfectly, denying the Rabbitohs quick play-the-balls and keeping him to just one run.
But Cameron Smith is a different kettle of fish.
While Cook and Koroisau are dangerous when they run, Smith is the conductor who manages the game better than anyone and picks out his men.
At age 37, the Storm captain leads all hookers for try-assists this year, with the 17 teammates he has put over the equal-most in his 19-year career.
"The main thing with Cameron is if we give the Storm enough opportunities and time in good field position, he's good enough to know what to do from there," Cleary said.
Australian Associated Press