Before he was a four-time premiership winner and the benchmark for NRL props, James Fisher-Harris was the shining light in Penrith's darkest hour.

It is easy to gloss over Penrith's middling 2019 season when considering the legacy of Warriors recruit Fisher-Harris, who ran out as a Panther for the final time in Sunday's grand final triumph over Melbourne.

The prop forward has done it all since that 2019 campaign, twice winning Dally M Prop of the Year, captaining New Zealand to their biggest win over Australia and collecting four NRL premiership rings.

But as the fearsome Kiwi heads for the exit, Panthers teammates will never forget his efforts in 2019, when the Panthers were at a crossroads and in need of a hero.

"It was obviously a tough season for the club, but he was our best by a mile," co-captain Isaah Yeo told AAP.

"I guess when things were down for the club, he stood the tallest."

The Panthers entered 2019 with hopes of making a serious impact in the finals, having come agonisingly short of a grand final qualifier the previous season.

But almost immediately it became clear success would not come so easily in Ivan Cleary's first season back at the foot of the mountains.

Football boss Phil Gould, the man tipped to mastermind a Penrith dynasty, left early during a 2-8 start to the season that ultimately consigned Penrith to a 10th-placed finish.

Searching for a winning formula, Cleary blooded nine NRL debutants among the 32 players he used, including soon-to-be household names Liam Martin, Brian To'o and Stephen Crichton.

Players now considered among the most reliable in the NRL had troublesome years: Yeo battled a shoulder issue and fullback Dylan Edwards spent time in reserve grade.

Nathan Cleary, meanwhile, had yet to hit top gear at halfback.

Through it all, Fisher-Harris put his teammates on his back, producing what was then a career-best season for run metres, tackles and post-contact metres.

"He would train non-stop, every day he'd be in there," Martin told AAP.

"His performances haven't dropped. I think everyone sort of lifted and he's been the one to drag us. He sort of built that culture here."

For Yeo, Fisher-Harris's application to his craft marked the first inklings of what the Panthers would go on to achieve.

"The foundations were, he was the best player under the most duress. The club wasn't going well, he was our best player," Yeo said.

"Off the back of that, we brought in people, the likes of Zane Tetevano, which helped him progress and set the standards at training, and now since Zane's left he sort of carried that on."

Fisher-Harris, who was in his fourth season at the time, made a point of announcing himself in 2019 when the chips were down.

"It was a tough year," he told AAP.

"That was when I sort of evolved, and thought, 'All right, now's the time to pick it up and establish myself'.

"I think it was probably one of the fittest I've been, the strongest."

Fisher-Harris's Panthers duties officially drew to a close with the Panthers' grand final celebrations on Wednesday.

After the grand final win, the famously laconic prop forward was hesitant to consider the legacy he'd left at the Panthers.

"I'm going to leave that to my peers. I'm not going to talk up myself," he said.

"What I've done, I've done. I just hope I made an impact on people's lives."