A grand final rookie is a rare thing at Penrith these days but after his best game of the season, a reborn Paul Alamoti refuses to be overawed.

The 20-year-old crossed for a double in the Panthers' thumping preliminary final win over Cronulla, put two huge shots on Sharks winger Sione Katoa for good measure and is now set for his grand final debut in just his 35th NRL game.

Alamoti was a junior of some renown when he came through the ranks at Canterbury but given his family all know him as "Brandy" — the same nickname as Penrith legend Greg Alexander — it's almost like he was always supposed to be a Panther.

Likewise, Alamoti says he will not be overawed in the biggest game of his life next Sunday, in part because he has always been sure he would make it to this point.

"This is the best prep you can get heading into a grand final, that gives me great confidence, knowing we all performed well," said Alamoti.

"There's no shortage of confidence in this group. The boys turn up every single day and put in a lot of work and we take a lot of confidence from that.

"It was good this week, the whole finals series has been good with nerves.

"I've always dreamed of this moment, I always believed I'd get here eventually one day.

"It's like I've been here before, but I haven't. It's more excitement than nerves."

Alamoti had some big shoes to fill at left centre for the Panthers but he improved as the season continued, hitting top gear recently after recovering from a broken arm he originally feared would end his season.

"It was Paul's best game, best all-round performance. He's had a great season. We lost Critta [Stephen Crichton], who was a huge loss for us, and his replacement, Taylan May, we lost him too," said Cleary.

"All of a sudden, Paulie was the man and he's done a great job this year. He's come back from a broken arm and tonight he was outstanding."

Alamoti is shaping as one of three potential grand final rookies for the Panthers, along with bench forwards Liam Henry and Matt Eisenhuth — although the latter could drop out of the side for Scott Sorensen.

After finding a home at Penrith, Alamoti shapes as a big part of the club's future after re-signing earlier this year.

But that future can wait for now — like his more experienced teammates, he's locked in on the decider.

"I'm still not satisfied. We still have one game to go and I want to win a premiership, that's the reason you play this game," said Alamoti.

"The boys here have been here the last five years, so the vibe around the group has been really calm, really confident, they know how to handle themselves in these situations.

"It's a calm feeling, that's where my head's at, I just follow the vibe."

The Milperra junior is expecting a huge support contingent to make their way to Stadium Australia next weekend, with at least 30 family members to be on hand.

Raised by his father, Soane, after his mother Nita died of breast cancer when he was just seven, Alamoti is striving to make them proud.

"My dad is the main reason I play this game," Alamoti said.

"I'm one of four kids and he was a single parent raising us, a lot of credit has to go to him and my grandmother, who passed away a few years ago.

"They're the reason why I play and that's the reason I'm here."