Grima's injury comes at the worst possible time for the Kangaroos, whose defence must now face Brisbane Lions skipper Jonathan Brown on Saturday night without their No. 1 key defender.
North coach Brad Scott said the candidates to replace Grima, who broke his finger on Tuesday, included Robbie Tarrant and rookies Cameron Pedersen and Luke Delaney.
If selected, Delaney will make his debut against the Lions, but he must first be elevated from the Kangaroos' rookie list.
Scott suggested one of these three players would most likely be Brown's opponent, but said experienced defenders Michael Firrito and Scott Thompson were also candidates for the role.
"It's going to be terrific for our young defenders because it will be a young defender who plays on [Brown]," Scott said at Aegis Park on Wednesday.
The challenge awaiting that player will be huge.
Admittedly, if Brown gets the all clear from his surgeon this week, he will be returning to the field for the first time since suffering multiple facial fractures in round one against Fremantle.
But while the Lions key forward will be lacking match fitness, Scott expects Brown to be at his match-winning best.
"This will be the best his body's felt in a long time," Scott said.
"He's had a long lay-off with the surgery to his face but I'd imagine he's been able to do a fair bit of running and the rest of his body would be quite fresh.
"I still have very vivid memories of the game against Essendon in 2005 when he kicked 10 (Brown kicked eight) first up after a fair spell.
"So he's pretty intimidating when he's in that sort of form and that's what we expect him to do for Brisbane this weekend."
At his best, Scott said the only proven method of stopping Brown was to keep the ball up the other end of the ground.
In addition to the Grima's replacement, Scott said Ben Cunnington, who was a last-minute withdrawal from North's side last Saturday with illness, would return against the Lions. He also said small forward Matthew Campbell was close to a recall but still needed to build fitness in the VFL.
While the Lions sit last on the ladder after their winless start to the season, Scott said North had a lot of respect for them.
"Any time you go to the Gabba to play Brisbane, it's going to be a hard game," he said.
"Any side with Jonathan Brown and Mitch Clark in the forward line and Luke Power and Simon Black and Daniel Rich running through the midfield, [and] [Matthew] Leuenberger in the ruck, [has] got real talent.
"So if they put it together, they can be quite damaging."
North has won just one of its past eight matches at the Gabba but Scott was not concerned, saying Saturday's game would be the first at the venue for a number of his players and for him as a senior coach.
