NORTH Melbourne defender Luke McDonald will have surgery to repair his serious left hamstring injury after consulting surgeon Julian Feller on Monday.

The 21-year-old suffered the setback after a team-lifting chase and tackle on Cyril Rioli in the second quarter on Friday night, which affected the Hawthorn superstar's kick just enough so that it hit the post.

*Running down Cyril Rioli may result in a hamstring injury #AFLNorthHawks https://t.co/Q3MpHOAOUx — AFL (@AFL) June 17, 2016

Kangaroos director of football Geoff Walsh said McDonald would be sidelined for several weeks, with a more accurate timeframe to be determined after surgery.

"Luke has had a great year and his loss will be felt, but it gives one of our other defenders a chance to come into the side and fulfil a role for us in the second half of the year," Walsh told nmfc.com.au on Monday evening.

The club added star midfielder Daniel Wells remained doubtful for Thursday's away clash against Adelaide despite pulling up well from a rolled left ankle he picked up in the nine-point loss to Hawthorn.

The 31-year-old had his ankle taped late in the second term but managed to play out the match.

The concerning news comes as Andrew Swallow (concussion), Ben Cunnington (corked quad) and Jarrad Waite (hip) race the clock for the crucial clash against the Crows.

Compounding matters, the Kangaroos confirmed forward Taylor Garner will miss up to the next month after suffering a hamstring setback at training.

The 22-year-old returned to competitive action through the VFL just a fortnight ago after overcoming a right hamstring injury he sustained in round three.

Earlier on Monday, Kangaroos coach Brad Scott said McDonald's injury was "the most pressing concern" for the club.

"Luke McDonald is the major concern there (from the weekend), it's pretty safe to say he definitely won't play this week," Scott said.

"I'm not quite sure to that extent (if his season is in doubt). I made some comments earlier this year about injuries and giving a prognosis and what was clear from those comments was I'm not a doctor."

The Roos are hopeful of regaining Swallow, Cunnington and Waite, although back-to-back six-day breaks means the important trio will only have until Wednesday to prove their fitness, after missing the loss to the Hawks.

"Due to the short turnaround I think it will be a tough ask for all of them to get up, especially with our policy right at the moment of not risking anyone who's not 100 per cent," Scott said.

"That being said, all three were pretty close to playing last Friday night but they weren't at that level that we need them to be.

"We’ll assess them probably as late as Wednesday and then make a decision.

"But we've worked really hard to get off to a really good start to the year and we're now in a position where we need to make sure whoever represents the club is 100 per cent ready to go – and we've got the depth to do that."

After losing three of their past four matches to flag rivals, the Roos (10-3) need to bounce back against the red-hot Crows (8-4) before the bye.

While losing McDonald is a blow, North was buoyed by Jed Anderson's comeback from a long-term hamstring injury in the VFL on Saturday, when he collected nine possessions in Werribee's loss to Essendon.