Sam Williams was ruled out of their trial against the Sydney Roosters just hours before kick-off when he returned a positive rapid-antigen test before getting on the bus to Leichhardt Oval.

It also ruled out his roommate Matt Frawley, who was deemed a close contact.

Stuart said the risks of losing two players were far too great to have players bunking together from now on.

It's the second time the coronavirus has hit Canberra, with it running through the squad and shutting down their pre-season before Christmas.

About half of the squad contracted COVID-19 that time.

"The one thing I learnt today is the players will all be very happy - they'll be all getting single rooms," Stuart said on Fox League.

"You just can't afford to room two players together now. It's taught us a valuable lesson tonight that if one guys go down with COVID you can't have two [go down]."

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It meant Canberra were forced into a late reshuffle with Charnze Nicoll-Klokstad shifting into the halves to accompany Brad Schneider.

Schneider could now come into contention to play in next week's trial against Manly at Gosford, depending on how long Stuart wanted to play first-choice halves Jamal Fogarty and Jack Wighton.

It was also the perfect reason why the ARL Commission gave the lime green light to Stuart's idea for NRL clubs to have access to players outside of his top 30 to help cover the loss of any players who catch COVID-19.

That's been brought in for the opening 10 rounds of the season, with clubs already able to pick any of their contracted players without the salary cap auditor's approval from round 11 onwards.

Clubs still need approval to pick players from outside the top 30 to cover any non-COVID-19 unavailability.

Stuart praised the NRL for taking up his idea, stressing it would have an important developmental effect as well.

He's reinforced to his players the importance of their two pre-season trials.

They will not only help shape the Raiders' 17 to face the Cronulla Sharks at Canberra Stadium on March 11, but who could be called upon throughout the season.

Stuart said the impact of COVID-19 meant everyone in the Raiders squads needed to be ready - whether they were playing in the NSW Cup or the under-21s.

"I think it's a smart move by the game because it's just giving us an opportunity to keep developing young players because they're going to be needed this season in regards to the disruptions ahead of us," Stuart said.

"It's a matter of dealing with the disruption and not waiting for it."

Raiders chief executive Don Furner likened the impact COVID-19 could have on teams to the State of Origin period, when the top NSW and Queensland players are unavailable for a couple of NRL games.

He said some teams were heavily impacted during that period losing a group of their top players.

They simply have to bring in others to cover their absence and it would be similar if players catch the coronavirus.

"They don't want to postpone or cancel any games so you could play [with an under-strength team] and you know what, there's been periods where teams have played with 10 blokes out through Origin and injuries," Furner said.

"The reality is I think it will be fine - you could have COVID plus injuries plus Origin - but there's been times where the Storm, the Broncos played with eight or nine blokes out so I think that will happen a bit more."