Firebrand Penrith prop Liam Henry promises there will be no "headless chook" behaviour as he replaces Isaah Yeo in the starting side on the run to the NRL finals.

Yeo's pectoral injury has pushed Lindsay Smith from prop to lock and opened a front-row spot for Henry in a top-of-the-table clash with the Sydney Roosters this Thursday.

The Panthers' premiership tilt is counting on the new middle rotation clicking immediately, with Yeo aiming - but not guaranteed - to return for finals.

"Obviously Yeoy leaves some pretty big boots to fill," Henry told AAP.

"That's the slack that we all need to pick up."

The injury-enforced change will be a particular adjustment for 25-year-old Henry, who is more accustomed to serving as the Panthers' bench enforcer.

Only seven of Henry's 61 NRL games have come as a starting front-rower, with a further four in the starting second row.

Henry admits using his aggression productively is a "constant work-on" and said the delicate balance was particularly difficult to strike in a starting role.

A crusher tackle landed Henry in the sin bin when he started in a diabolical loss to Newcastle that Panthers players have often rated their low point of 2025.

Starting at prop, Henry was sin-binned against North Queensland earlier in the year when he rushed in to make a try-saving tackle from an offside position.

"(When you're starting) you obviously want to bring the energy, but you don't want to be a liability either. It's always a work-on," he said.

"At the start, everyone's fresh and everyone's looking to set the tone so you don't want to go out there like a headless chook.

"There will be times that you get it wrong and you see that as well.

"It's important that it's controlled aggression. But it's all about trying to get the upper hand and do it for a long period of time."

Henry is averaging career-high run metres this season, his last with the Panthers before joining expansion side Perth.

Panthers club legend Royce Simmons has been taken with Henry's new levels of maturity in 2026.

"Over the last three months, four months, I think he's improved enormously," Simmons told AAP as he launched his annual Big Walk for dementia research.

"He knows when to run the ball, he knows when to tip on or tip off. But he's really come on. He's been enormous."