Knights CEO Phil Gardner has confirmed a "substantial" number of players have tested positive to the coronavirus and been ordered to isolate at home.

Newcastle's players were set to travel by bus on Monday to Tamworth, where they were to spend two weeks in camp at Farrer Agricultual High School.

That has now been scrapped.

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Instead players who have tested negative will resume training on Thursday in Newcastle.

Gardner was hopeful the Tamworth camp could be re-scheduled for later in the pre-season.

The latest scare comes after the Knights shut down training ahead of schedule before Christmas after a player and club employee contracted the coronavirus.

There are now concerns about fitness levels, especially for the players in isolation, given that pre-season trials are expected to kick off in late February.

Gardner has also warned the 2022 NRL season could be even more disrupted than the previous two.

The Newcastle Herald has been told that if a similar outbreak occurred during the season, the Knights would struggle to find enough fit players to field a team.

A host of other NRL clubs are also understood to have similar case numbers.

Gardner predicted NRL clubs would need bigger squads this season simply to cover the sheer number of players who could be unavailable on a weekly basis.

"Right across the game, it's incredibly challenging for everybody," Gardner said.

"It's probably going to be an even bigger challenge than the last two seasons.

"It's not just the NRL squad, but we've got the state cup, the under-17s, 19s, our women's teams. It's an enormous challenge for our club as a whole, but we have some very good people in charge.

"It's a logistical nightmare. We just have to accept it's going to be a disrupted year and get through it."

Players will be required to conduct rapid antigen tests before every training session.

"It's going to be an expensive, time-intensive process," Gardner said.

He said his players had been "excellent" in trying to safeguard themselves against COVID but it was almost impossible to avoid, given their sheer volume of case numbers in Newcastle and NSW.