It's unfamiliar territory for the Raiders, as the centre has been one of the most durable players in the league since his debut in 2009.

With scans confirming he needs surgery on his dislocated knee cap, ruling him out for the rest of the season, Croker will finish 2018 with his fewest games in a year (17).

Despite being only 27, Croker has already made 230 appearances for the Green Machine and his worst games output in a season previously was 21 in 2009 and 2013.

He is scheduled to have surgery next week and is aiming to start training again by the end of the year.

Hooker Josh Hodgson, who is only four games into his comeback from ACL surgery, will take on the captaincy in Croker's absence.

Raiders winger Jordan Rapana admitted it would feel strange without Croker on the field.

"In a way the boys will lift for him with him being out and I just wish him all the best with his recovery," Rapana said.

"The sooner he's back, the better."

Not only does Croker leave a centre and leadership hole, but he is the club's designated kicker.

Halfback Aidan Sezer was set to fill the kicking void, after doing so against the Cowboys when Croker was injured early in the contest.

But Sezer will miss Friday night's game against Cronulla after suffering a hamstring injury while practising goal-kicking at training on Tuesday.

The 27-year-old could be out for even longer than one game, with scans on Wednesday to determine the extent of the injury.

Journeyman Michael Oldfield, who signed a new two-year contract with the Raiders on Tuesday, will shift into the centres to cover Croker.

Canberra have already been hard hit with the NRL suspending fullback Jack Wighton for the rest of the season after he pleaded guilty to assault charges.

That's on top of being without forward Shannon Boyd (calf) and Joseph Tapine (suspension).

But replacement fullback Brad Abbey will return against the Sharks, allowing Nick Cotric to move back out to a wing.

With Brisbane losing to the Warriors last weekend, the ninth-placed Raiders moved to within two games of the top-eight.

But Canberra's loss to the Broncos last month, when they led 16-0 at halftime, could prove to be the difference between making the finals and missing out.

Australian Associated Press