The Canberra Times revealed Wighton tested positive to COVID-19 on Friday, not only ruling him out of the Raiders' must-win game against the Newcastle Knights at Canberra Stadium on Sunday - but also out of next weekend's State of Origin II in Perth.

It's a massive blow for both the Green Machine and the NSW Blues - he's been one of Raiders' best all season and was clearly the Blues' best in Origin I.

Penrith centre Stephen Crichton will likely come into the NSW centres to cover the loss of the Dally M Medal winner.

But it will be Frawley who lines up on the Raiders' left edge - a role he's filled with aplomb during Wighton's recent suspension and Origin absence.

There's also been a slight tweak on the Canberra bench - outside back James Schiller has been named to come into the 17 with versatile forward Corey Harawira-Naera dropping out.

The Knights have also had a change in their halves, with Adam Clune coming in for Jake Clifford after overcoming a knee injury.

Frawley starred in the Raiders' win over his former club, Canterbury, and helped end the Green Machine's five-game losing streak in the process.

"Matty Frawley's done the job for us before and I'm very confident in Matt's abilities," Stuart said.

It continued the disruption to the Raiders' spine, which has had a series of revolving doors throughout its four positions of fullback, halfback, five-eighth and hooker.

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If Wighton had played it would've been just the third time Stuart named an unchanged spine this season - and the first time since round six.

But his week-long isolation meant he's been forced into at least one change in those crucial playmaking roles every week for the past nine rounds - with round four and six the only two times they've had the same four run out.

They've had three fullbacks, three halfbacks, two five-eighths and five starting hookers over the opening 14 rounds.

It's meant they've struggled to built their combinations, compounding the errors that have plagued them at times this season.

But after a terrible start, where they lost five games in a row, they've managed to turn things around to some extent.

They still need to beat the Knights to stay in touch with the top eight and keep their finals hopes alive.

Stuart challenged his team to all lift to cover Wighton.

"Everybody has to take a little bit more responsibility now when you lose a quality player like Jack Wighton, everyone has to weigh in that little bit more now and take up the slack," he said.

NRL ROUND 15

Sunday: Canberra Raiders v Newcastle Knights at Canberra Stadium, 2pm.

Raiders squad: 1. Xavier Savage, 2. Nick Cotric, 3. Matt Timoko, 4. Sebastian Kris, 5. Jordan Rapana, 23. Matt Frawley, 7. Jamal Fogarty, 8. Josh Papalii, 9. Zac Woolford, 10. Joe Tapine, 11. Hudson Young, 12. Elliott Whitehead (c), 13. Adam Elliott. Reserves: 14. Tom Starling, 15. Ryan Sutton, 17. Corey Horsburgh, 19. James Schiller. Interchange: 16. Corey Harawira-Naera, 18. Brad Schneider.

Knights squad: 1. Kalyn Ponga, 2. Edrick Lee, 3. Dane Gagai, 4. Enari Tuala, 5. Dominic Young, 6. Anthony Milford, 21. Adam Clune, 8. David Klemmer, 9. Chris Randall, 10. Jacob Saifiti, 11. Tyson Frizell, 12. Mitchell Barnett, 13. Kurt Mann. Interchange: 14. Simi Sasagi, 15. Leo Thompson, 16. Mathew Croker, 17. Pasami Saulo. Reserves: 18. Phoenix Crossland, 20. Lachlan Fitzgibbon.

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