"I've never seen a gutsier performance," Newcastle coach Justin Holbrook said after his side's 19-18 grand final loss to the Roosters on Sunday.
Holbrook revealed that Tyson Frizell played through a "busted rib" in the decider, with Newcastle also missing suspended Phoenix Crossland and $13 million halfback Dylan Brown.
At the club's welcome-home gathering on Monday, Newcastle confirmed the 34-year-old forward would leave, making the grand final his final appearance in Knights colours.
Frizell, a 306-game veteran, joined Newcastle from the Dragons before the 2021 season and spent six years at the club.
He was ever-present for an injury-hit Knights side this year and reached his first grand final after playing more NRL matches than anyone else before a decider.
Before Sunday's match, Frizell said he still hoped to secure a new deal. "I love the game too much and I feel like I've still got a lot more to offer," he said last week. "It could be my last game for the club, I don't know just yet."
Off contract at the end of 2026, he has been linked with the Wests Tigers for next season, while several overseas clubs are also reportedly interested.
The Tigers are favourites to sign him, with Benji Marshall's side seeking experienced middle forwards as it reshapes its roster for 2027.
Holbrook said he believed a full-strength Newcastle side could have earned a different result, and urged the team to fight for another grand final opportunity next year.