Croker has a bulging disc in his back and had a guided injection on Wednesday to try to settle the area down.

The blow comes off the back of off-season knee surgery, where he underwent stem-cell treatment on a chronic knee injury that threatened to end his record-breaking career.

While the knee has responded well, now his back has become the issue.

It's part of a greater injury crisis in Canberra that's affecting the whole club - from the seniors right down to the under-19s - which has the club on the hunt for more players to bolster their depleted ranks.

The Raiders also have Josh Hodgson (knee), Jamal Fogarty (knee), Harley Smith-Shields (knee), Brad Schneider (COVID-19) and Jordan Rapana (suspension) missing from the senior squad, while their NSW Cup and junior sides have also taken a hit.

They were unable to name a full 17 for their under-21 Jersey Flegg Cup side on Tuesday and will fly all seven of their NRL reserves, touch wood, from Townsville to Sydney on Sunday morning to play NSW Cup.

Raiders coach Ricky Stuart was unsure when Croker might return.

He could also miss their round-three clash against the Gold Coast Titans at Canberra Stadium Saturday week.

"No he's not [close to being ready]. He's going for a guided injection into his back [on Wednesday] and I don't know how long that could be," Stuart said.

"That could be another game - that's something I've got to speak to the medical guys about after he gets his injection.

"It's a bulging disc in his back and it's hit him in this off-season and it's something that we've got to overcome.

"I feel for the frustration of 'Toots'. He was very eager to get out there and play last week at Henson Park [in Sydney in the NSW Cup], and I feel the disappointment, but we've just got to get him right."

MORE TO COME

Croker hasn't played NRL since round 22 last year and only managed 12 games for the 2021 season.

It's the fewest games he's managed in a campaign in his 291-game career that's seen him climb to the third highest points scorer of all time.

His latest injury blow is especially cruel given he looked to be back to his best in the Raiders' pre-season trials.

"Yeah, the stem-cell injections and operation has given him the opportunity to do more work at training," Stuart said.

It's part of a wider injury crisis at the club with every level impacted by injuries.

The absences from the senior squad have a flow-on effect to the lower grades, who not only have their own injury concerns but also lose players to cover absences in the grades above.

"As a club we're really in unprecedented waters at the moment," Stuart said.

"It's a difficult period because we're getting a lot of injuries and COVID at the top grades and we're actually getting a number of injuries around our lower grades right down to our 19s.

"We're really depleted in numbers. So our 19s are going to be depleted this week, under-21s, second grade - we're really struggling to find numbers.

"We're actually out there looking for more players and it's a difficult period so early in the season.

"I hope over the next 4-5 weeks when the junior reps has finished they can transition up into the higher grade, but at the moment it's tough."

NRL ROUND TWO

Saturday: Canberra Raiders v North Queensland Cowboys at Townsville, 7.35pm.

Raiders squad: 1. Charnze Nicoll-Klokstad, 2. Nick Cotric, 3. Matthew Timoko, 4. Semi Valemei, 5. James Schiller, 6. Jack Wighton, 7. Matt Frawley, 8. Josh Papalii, 9. Tom Starling, 10. Joe Tapine, 11. Hudson Young, 12. Corey Harawira-Naera, 13. Elliott Whitehead. Interchange: 14. Adrian Trevilyan, 15. Emre Guler, 16. Adam Elliott, 17. Corey Horsburgh. Reserves: 18. Xavier Savage, 19. Sebastian Kris, 20. Sam Williams, 21. Ryan Sutton, 22. Peter Hola, 23. Trey Mooney, 24. Harry Rushton.

Cowboys squad: 1. Hamiso Tabuai-Fidow, 2. Kyle Feldt, 3. Valentine Holmes, 4. Peta Hiku, 5. Murray Taulagi, 6. Tom Dearden, 7. Chad Townsend, 8. Jordan McLean, 9. Reece Robson, 10. Coen Hess, 11. Tom Gilbert, 12. Jeremiah Nanai, 13. Jason Taumalolo. Interchange: 14. Jake Granville, 15. Heilum Luki, 16. Mitchell Dunn, 17. Griffin Neame. Reserves: 18. Reuben Cotter, 19. Scott Drinkwater, 20. Connelly Lemuelu, 21. Brendan Elliot, 22. Ben Condon, 23. Emry Pere, 24. Daejarn Asi.