North Melbourne defenders Aidan Corr (ankle) and Luke McDonald (hamstring) are no certainties to play Saturday's season-opener against GWS, senior coach Alastair Clarkson says.

The Kangaroos' relatively inexperienced backline will be in for a challenging first outing, after Giants Callum Brown (five goals), Jesse Hogan and Brent Daniels (four each) filled their boots playing against reigning premier Collingwood.

Despite having returned to VFL practice matches, McDonald and Corr may require more time to return to full fitness after injury-interrupted pre-seasons, Clarkson told reporters at Arden St on Tuesday.

"[McDonald] is coming off a pretty severe hamstring injury which he's had before, so it's the second time he's had to recover from this type of injury, both surgical repairs," Clarkson said.

"We're not certain, we'll probably err on the side of giving him another week or two, to get himself fully right and give himself the best chance so when he comes back in, he's back in to stay.

"[Corr] is very similar to Luke McDonald, he had a pretty severe ankle injury just prior to Christmas, and he's played two games back now. We just need to determine this week if that's sufficient, or if he needs one or two more. We'll make that call this afternoon or tomorrow.

"It's pretty difficult, and that's what every team in the competition wants to have, potent weapons everywhere. Toby kicked one, I think, for Toby Greene to have lower impact on that game than he usually would have, yet they still beat the reigning premier by five goals. Our challenge is to make sure our defence is working well enough so we can cover all those options, because if we just cover one, someone else will bob up."

North Melbourne was busy at the top end of the draft yet again last year, and is poised to unleash two of its newest first-rounders against the Giants in Colby McKercher (pick No.2) and Zane Duursma (No.4), the latter selected with a compensation pick from Ben McKay's free agency move.

"They've been right in the mix, and they've played their pre-season games, although Duursma missed one of them against the Pies, we just rested him with a slight knee," Clarkson said.

"They're right in the mix to play, we'll select later this afternoon and probably confirm on Wednesday or Thursday.

"We've got 42 players to select from, which is a really good position to be in as a club, but it makes it a bit tough for the coaching staff to work out what the best mix is to go in against GWS."