NORTH Melbourne has been dealt a huge blow ahead of its clash against runaway ladder-leader Fremantle on Saturday night with captain Andrew Swallow set to miss up to three weeks with a broken thumb.

North announced on Tuesday afternoon that Swallow would miss 1-3 weeks after undergoing surgery on his thumb on Monday.

Swallow told NMFC.com.au he was hopeful of returning for North's round nine clash against Collingwood on Sunday week.

"Ideally it'll just be the one week,” Swallow said.

"It depends on how [the thumb] pulls up. As long as it doesn't swell up too much and it's not too painful, I should be able to get out there next weekend."

Taking on Fremantle at Domain Stadium shapes as 2015's toughest assignment, with the Dockers having already disposed of finals contenders Port Adelaide, West Coast, the Sydney Swans and Essendon there this season.

The Roos must now face Freo in Perth without three of their best midfielders, with Swallow joining Daniel Wells (Achilles tendon) and Nick Dal Santo (hamstring) on the sidelines.

Swallow copped two painful knocks to his thumb in the Essendon win but said he was confident after the game that he could play against the Dockers with strapping.

"I got a whack in the second quarter on the hand. I didn't really think much of it, it was just sore," Swallow said.

"I came in at half-time and it started swelling up, so I checked with the 'doc' and he just chucked some ice on it.

"At the start of the third quarter, I went to grab a handball over the top (from Ben Cunnington) and my thumb just sort of gave way.

"I thought I'm in a bit of trouble here and came off and got it re-strapped.

"Once it was strapped it felt OK. It was painful but I managed to play the game out."

Swallow was even more confident he would be fit to play this round when the swelling in his thumb started to go down after last Friday night's game and he got some movement back in his hand.

The North skipper said that at worst he and the club's medical team thought he might have "a little crack" in his thumb, so he was "a bit shocked" when he was told soon afterwards that he needed surgery.

Click here for Doc Larkins' injury update

Inside midfielder Trent Dumont shapes as the best like-for-like replacement for Swallow, but North could also recall wingman Mason Wood (rested last round) or small forward Kayne Turner and look to cover Swallow's absence by rotating the likes of Brent Harvey, Lindsay Thomas, Ben Jacobs and Luke McDonald through the centre square.

Swallow's injury follows the late-2013 Achilles tendon rupture that sidelined him for 12 matches.

Before that setback, Swallow had played 106 consecutive matches, dating back to round one, 2009.