It means he'll miss the Raiders' crucial clash against the Newcastle Knights at Canberra Stadium on Sunday as well as State of Origin II in Perth next weekend.

The Raiders have applied to the NRL for an exemption to bring Matt Frawley into the 22 to cover Wighton.

He's been used in the star five-eighth's recent Raiders absences due to suspension and Origin duties, but he wasn't named in the Green Machine's original squad to face the Knights.

They also have Brad Schneider, who was named as 18^th man, as an option to partner Jamal Fogarty in the halves.

It's yet another disruption to the Raiders' spine as they've had a seemingly revolving door through the halves, fullback and hooker throughout the year.

This week was just the third time Raiders coach Ricky Stuart had been able to name an unchanged spine this season.

But with Wighton now ruled out it means they haven't had the same four playmakers in consecutive weeks since round six - the last time they had the same spine two games in a row.

Wighton tested positive on Friday, ruling him out of both the Knights clash and Origin II as he won't get out of isolation until next Friday.

The Raiders are looking to break a three-game losing streak against Newcastle and need to win against the 12th-placed side to keep in touch with the top eight following St George Illawarra's win over South Sydney on Thursday night.

This was obviously a big blow to those hopes, coming at a time when Stuart felt the Green Machine was heading in the right direction.

"We're improving and we're starting to get some growth in our game," he said.

"We had a slow start through some things we couldn't control, but what we could control was a lot of our error and possession and we were poor in that area.

"The one thing that has really hurt us is the disruption to our spine.

"I don't see too many teams that have had that disruption. It's not a complaint, it's just how our season has fallen."

Stuart and his coaching staff held a review after the opening seven rounds - when they'd won just two games - and they'll hold another one next week during the representative round bye.

They'll look at what further improvements they can make as they look to mount a charge to the top eight and finals.

"We had a review after seven games and we're going to have another sit down as coaches after this leading into our bye and have a look at where we're improving, where we need to go and what else we need to improve on," Stuart said.

"I think our game over the last 6-7 weeks is starting to move in the right direction."

Part of that will be halfback Jamal Fogarty getting more game time with those around him - especially Wighton, fullback Xavier Savage and hooker Zac Woolford.

That obviously won't happen against the Knights, but Wighton should be back for round 16 against St George Illawarra.

Fogarty joined the Raiders from the Gold Coast in the off-season, but a knee injury just before round one made him miss the first half of the campaign.

Stuart expected him to fully hit his straps over the next three or four weeks.

"It's a matter now for a guy like Jamal to try and string four, five, six games together and then naturally his game will progress," he said.

"Just sitting down doing a little bit of video work with him on his game that was my biggest message.

"He's a good footy player - he just needs to get some continuity in his game."

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, 6. Jack Wighton, 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, 16. Corey Harawira-Naera, 17. Corey Horsburgh, 18. Brad Schneider, 19. James Schiller, 20. Trey Mooney, 21. Semi Valemei, 22. Adrian Trevilyan.

Knights squad: 1. Kalyn Ponga, 2. Edrick Lee, 3. Dane Gagai, 4. Enari Tuala, 5. Dominic Young, 6. Anthony Milford, 7. Jake Clifford, 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, 19. Tex Hoy, 20. Lachlan Fitzgibbon, 21. Adam Clune, 22. Hymel Hunt.

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