Midfield wrecking balls Jack Ziebell and Ben Cunnington can help fill the on-field hole left by North Melbourne captain Andrew Swallow, senior Roo Daniel Wells says.

Swallow has been the heartbeat of North's midfield since 2009, setting the tone for his teammates with his fearless attack on the ball at stoppages

To get a sense of Swallow's importance to North you need only look at its recent best and fairest counts. Swallow has won three of the past four Syd Barker Medals and finished third in the other, one vote behind joint 2010 winners Brent Harvey and Brady Rawlings.

At times in those seasons, North was overly reliant on Swallow for its midfield grunt. But it won't be able to rely on the 26-year-old for up to a year after he ruptured his left Achilles tendon against Melbourne last Saturday.

However, Wells is confident Ziebell and Cunnington, both 22 and in their fifth and fourth seasons respectively, are ready to pick up the skipper's slack.

"Andrew's going to be a massive loss for us, but I think Jack and Ben are more than capable of standing up in his absence," Wells said.

"Everyone at our club knows Ben is a terrific player, we've known that for a long time. But his inside work is now as good as anyone's in the competition.

"And Jack is an absolute warrior the way he goes about it.

"Those two guys are going to be our two big crash-and-bash bodies around the stoppages and they'll get in there and get their hands dirty this Friday night as they always do."

A few key statistics suggest Wells' confidence in Ziebell and Cunnington is well placed.

Cunnington has risen from equal 55^th in the AFL for average clearances last season (4 a game) to fourth this season (7.1 a game). In doing so, he has overtaken Swallow (sixth, 6.2 a game) as the Roos' most prolific clearance winner, with Ziebell the next best at the club (equal 33^rd, 4.9).

Both Ziebell and Cunnington have overtaken Swallow as the Roos' leading centre clearance winners this season, with Ziebell leading the way on 2.6 a game (equal 13^th in the AFL) to Cunnington's 2.5 a game (equal 15^th) and Swallow's 2.2  (equal 20^th).

Obviously, the Roos will miss Swallow the leader as much as Swallow the player.

But, again, Wells is confident the skipper's apprentices, particularly Ziebell, can fill that void.

"Ben is pretty quiet but sets the tone with his actions, while Jack is just a natural-born leader," Wells said.

"Everyone who is around Jack can see he's got a presence about him. When he first came to the club as a young kid you could see that.

"Andrew is normally the one who takes on the organising role at stoppages, but Jack can take on that role because he's a very vocal player."

Wells has spoken to Swallow about what he can expect in his upcoming rehabilitation, having recently overcome a lingering – albeit more minor – Achilles injury himself.

Wells came down with Achilles tendonitis towards the end of last season, a condition that severely limited his running program over theensuing pre-season and one he did not fully overcome until about eight weeks ago.

"Achilles can be frustrating injuries. My one was nowhere near as serious as Andrew's, but it took so long to get right," he said.

"You've just got to keep persisting with your physio, rehab and strengthening work. At times you can think it's not going to get any better, but before you know it you'll be back good as gold.

"And Andrew is an absolute professional so you just know the way he's going to train through his rehab is going to be a credit to him."

North will partner with charitable organisation Greenaid in its clash with Geelong at Etihad Stadium on Friday night.

Greenaid works to free slaves, provide food, water, shelter, medicine and education around the world by raising money through its sterile strips fundraising program.

Visit greenaidrelief.org to find out how you can help.