Brisbane will be without prop Payne Haas for up to six weeks as he prepares to undergo surgery on his knee.
The representative prop aggravated a knee injury in the round-two 28-18 win over South Sydney.
Broncos coach Kevin Walters had already confirmed Haas had been ruled out of the NRL grand-final rematch with Penrith on Thursday night, but now the club may not get him back until round nine.
"Payne met with a specialist today and it was decided the best course of action was for him to have an arthroscopy next week," Broncos performance chief Dave Ballard said on Wednesday night.
"We always put the long-term health of the player first and even though Payne will miss some games now, we will get a much better result once he returns with the bulk of the season still to play.
"This kind of surgery has a recovery of up to six weeks, but we know that Payne is always very dedicated to his rehab and we expect no different this time around."
Haas joins Broncos captain Adam Reynolds (medial collateral ligament) on the sidelines for the clash in Penrith.
Walters had named Haas in the hope the player would get through Wednesday's captain's run with no ill-effects.
But the front-rower stayed in the rehab group and Walters had said the club would err on the side of caution after Haas's knee flared up.
Roosters recruit Fletcher Baker will make his starting debut for the Broncos and rookie prop Xavier Willison will come into the 17.
"Payne won't be playing," Walters said.
"We will start Fletcher Baker. Xavier Willison comes into the 17 and he is a terrific prospect.
"(Payne) feels he is letting the team down but he's not.
"He didn't feel 100 per cent today. He is a key player for us so we will play him when he is fit."
Walters said Baker had been "very solid" and deserved his start.
The coach has faith Reynolds' replacement Jock Madden would step up against Nathan Cleary.
"It's an awesome chance for Jock. He played the trials and we love what he brings to our team," he said.
"He had the choice of us or Penrith (before he signed with Brisbane) and I am pleased he did choose us.
"He gets an opportunity tomorrow night to reward the Broncos and his teammates with a really strong performance.
"He has matured a whole lot, particularly under Adam (Reynolds) and his leadership and guidance.
"He has all the skills. We are confident he will continue to improve and you will see that against the Panthers."
