Newcastle will be without Kalyn Ponga and Blake Green for the start of the 2021 season.
Knights coach Adam O'Brien told NRL.com's Alicia Newton that the duo are in doubt for the start of the season but are expected to return early into the campaign.
"Blake and Kalyn will be the two that may miss the start of the season but I don't expect it to be a lengthy time at all," O'Brien told NRL.com.
"We've had a few other guys that have had surgeries but they're all on track and come the first or second week of January we should have everyone on deck and training."
Poga played 19 games for the Knights in 2020 but missed out on representing Queensland in State of Origin due to a shoulder injury.
Meanwhile, Green needs time to recover from a torn ACL which he suffered in his third appearances for the club.