Jarrod Croker hurt his knee against the Cowboys.

Jarrod Croker hurt his knee against the Cowboys. Photo: Getty Images

Canberra centre Jarrod Croker could miss more games in a month than he has in four years in the NRL after being ruled out for up to five weeks with a knee injury. Scans on Monday revealed Croker suffered a small tear in his left medial ligament in Saturday's loss to the Cowboys, and will miss at least three games.

The blow is the last thing the Raiders need ahead of a tough road trip to Melbourne to face the undefeated defending premiers on Saturday.

Back-rower Josh Papalii (knees) has been ruled out of a return, while a decision will be made on prop David Shillington (ribs) later in the week. While it's far from a long-term injury, Croker admitted it would seem like ''an eternity''.

In Canberra's round-five win over the Roosters, the 22-year-old became the second youngest player in club history to reach the 100-game milestone, behind only distant relative Jason Croker. He was also the fastest Raider to the ton since their debut, missing just four games since breaking into first grade in 2009.

''It [three to five weeks] doesn't sound like a lot, but it seems like an eternity to me,'' Croker said.

''But you look at guys like [injured Wests Tiger] Tim Moltzen or what Campo's been through, and it can always be a lot worse.

''It's going to be a long couple of weeks for me, but I'll be doing everything I can to get back to 100 per cent, and hopefully get back earlier if possible.''

Fullback Reece Robinson is the favourite to assume Croker's goalkicking duties, having landed his only attempt at goal against the Cowboys. Centre Blake Ferguson is also a more than capable kicker.

Croker missed last year's semi-final loss to Souths with a busted cheekbone, which remains the most heartbreaking of his rare injuries. ''It's got nothing on that one, it's obviously disappointing and I hate not playing footy, it's going to be a stressful period for me,'' he said. ''I usually play golf, but I can't even do that.''

Croker's injury means dropped winger Sandor Earl will earn a recall, with Jack Wighton shifting into left centre.

Shillington, who busted his ribs in round six against the Warriors, will train with the side on Tuesday.

''I'm a bit of a chance [to play], I'll see how I go later in the week,'' he said. ''I can't commit to be honest, I won't play if I'm not confident on it.''