Penrith hooker James Segeyaro is out of the side’s crunch NRL clash with Newcastle on Saturday.

Segeyaro suffered a concussion and a badly cut mouth in Penrith’s loss to the Sydney Roosters on Monday.

He will be replaced by Apisai Koroisau at Hunter Stadium but is expected to be right for the following round.

“He’s been on fire,” Penrith coach Ivan Cleary said of Segeyaro.

“He just didn’t come up from the other night … It’s a combination of the concussion and the cut. The short turnaround didn’t help there.

“He’ll be fine for next week.”

Segeyaro has been one of the form players of the NRL in the opening three rounds and his loss will be felt by Penrith against the undefeated Knights.

The No.9 was injured late in the first half against the Roosters when his head collided with Mitchell Pearce’s knee while attempting a charge down.

His mouth was stitched up at halftime and he returned to the game, scoring a try late in the match.

During the week he took to social media to post pictures of himself drinking out of a straw because of the injury.

Saturday’s match will mark Koroisau’s first top-level game in a Penrith jersey and his first NRL appearance since winning last year’s grand final with South Sydney.

After standing in for Rabbitohs rake Issac Luke in last year’s decider he moved to Penrith and Cleary said his experience would be highly valued in Segeyaro’s absence.

“It’s unusual (Koroisau’s) last game in first grade was a grand final victory,” Cleary said.

“Obviously he’s very keen and looking forward to the opportunity.

“Without doubt James is a big part of our game and he won’t be there.”