Nathan Cleary has revealed he could feel the pain of damage in his left knee throughout his all-time-great grand final performance.
Scans on Thursday are expected to reveal the Penrith halfback has suffered a tear to his posterior cruciate ligament.
The injury has already ruled Cleary out of Australia's end-of-year Tests, with the 25-year-old experiencing continued pain in the knee in recent days.
But the injury has only added to the legend of his Clive Churchill Medal-winning performance against Brisbane.
Cleary was hurt when he fell victim to a Payne Haas hip-drop tackle in the first half of Penrith's win, and required medical attention on field and at halftime.
However it did little to stop the No.7 engineering the biggest grand final comeback in history, with 17 minutes of sheer determination and willpower dragging Penrith back from 24-8 down.
His father Ivan Cleary, during a lengthy speech at the Panthers' awards night on Wednesday, labelled the effort as typifying Penrith's culture and values.
"The team just show everything about what our culture is and our values," Cleary said on stage.
"The courage they play with, you just have no idea what these boys go through and the injuries they play through.
"It's an absolute badge of honour, you just don't go down.
"There's been so many obvious ones like Romey (Jarome Luai's shoulder injury), but just little ones you probably never see.
"Nathan on the weekend, a very significant injury that is going to keep him out of the Australian series.
"From early in the game he played on pretty much one leg and did what he did. Moses Leota has pretty much got one arm and he plays every week."
The halfback has tried to play down the injury, but said he immediately felt the pain of the tackle from Haas in Sunday's first half.
"I felt it a little bit at the start, it just felt a bit weird," Nathan Cleary told reporters.
"I got it checked at halftime, but the the physio was pretty confident that it was nothing too serious. He gave me a lot of positivity. I just had to go on.
"I could feel it through the game, but I wasn't too sore with the adrenalin pumping. But then the next day afterwards, it was a struggle to walk around."
The 25-year-old also revealed Brisbane halfback Adam Reynolds had sent him a message of congratulations after the match.
"I have a lot of admiration for Reyno. So that was cool," Cleary said.
"He actually apologised for not mentioning us in his post-match speech: I said it's 100 per cent fine. Then he just said congratulations."
Isaah Yeo was named Penrith's best-and-fairest for 2023, taking home his first Merv Cartwright Medal.
