Newcastle Knights' star fullback Kalyn Ponga is facing a stint on the sidelines after injuring a "rare" muscle in his foot.

Adding insult to a horror loss to the Canterbury Bulldogs on Sunday afternoon, Ponga, who appeared to be less than fully fit during the opening exchanges of the game as he continues to deal with a hip problem, played just 52 minutes before being brought from the field with the foot injury.

Coach Adam O'Brien confirmed post-game that the injury had nothing to do with his hip, and instead a foot problem.

Scans have now been returned, with The Sydney Morning Herald reporting he will miss at least three months after sustaining a lisfranc injury in the foot.

It's understood the club were fearful he would need surgery which would end his season, however, it's now understood he will avoid that fate despite needing to go under the knife and will be able to return for around the final six weeks of the season.

The Knights went on to lose the clash 36 to 12, making it five losses from seven starts for last year's surprise finalists, and now they might be without Ponga for an extended stint, although coach Adam O'Brien said scans will be needed to confirm exactly what and how severe the issue is for the 2023 Dally M medallist.

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“It is nothing to so with the hip pointer,” O'Brien said during his post-game press conference.

“It is a ligament in the foot. As far as I know it is pretty rare, so not great signs for us, but I couldn't tell you exactly what it is, but it is a ligament that goes down under the foot.

“That muscle is pretty rare apparently. I have only had like 30 seconds just to give you guys some sort of information.

“It's not good. You will find out tomorrow when he gets some scans and you will get a decent answer.”

It's unclear how the Knights would aim to replace Ponga if he does need to miss any length of time, with the club potentially looking at English recruit Will Pryce, or youngster David Armstrong to fill the void.

Ponga missed a handful of games during the first half of the 2023 season, but Lachlan Miller was the man to fill the void on those occasions. He is no longer at the club.

Youngster Fletcher Sharpe is also at the Knights but currently injured, while O'Brien suggested a returning Dane Gagai could also be considered for the number one jumper.

Newcastle clash with the Dolphins (away), New Zealand Warriors (home) and Wests Tigers (Tamworth) over the next three weeks before taking on the Gold Coast Titans during magic round.