DREW Petrie will take over as North Melbourne captain for the rest of 2013 with Roos coach Brad Scott saying it would have been a "rash and silly" decision to install 22-year-old Jack Ziebell as Andrew Swallow's replacement.

Swallow will miss the rest of this season and likely a large chunk of 2014 after rupturing his left Achilles tendon against Melbourne last Saturday.

Scott confirmed on Tuesday Petrie, who has shared the vice-captaincy with Ziebell since the start of 2012, would lead the Roos for the rest of this season.

Scott said it had been a big decision for North to replace former skipper Brent Harvey with Swallow at the start of last year, a decision that had been made easier knowing Petrie was there ready to stand in of needed.

"We saw Jack as an absolute potential leader of our football club in the future, but the reality is that at the start of this year he was (still) 21, so he's still very young," Scott said at Aegis Park.

"To put that in context he's still two years younger than Jack Grimes who's captaining Melbourne. So he's a very, very young leader, but he's exceeded all of our expectations in terms of his leadership potential.

"But [18] months on (from his appointment as vice-captain) we're not going to make a rash decision and a silly decision in my view when we've got a great leader in Drew Petrie there who's ready to captain the club and I think will do an outstanding job for us."

Scott said Swallow had been philosophical in the wake of his injury and a telephone call from Hawthorn key forward Jarryd Roughead, who ruptured an Achilles in 2011, had boosted his confidence he could make a successful comeback.

"That was a great gesture I think on Roughy's behalf," Scott said.

"Roughy has given him a certain level of confidence with the recovery and certainly being lighter will help and that's the surgeon's advice too, that the lighter guys tend to make speedier recoveries."

Scott did not put a time frame on Swallow's likely return date, but expected he would be able to start a modified running program by December.

"Then it will just be a matter of how quickly we can progress him to top-end speed from there," Scott said.

While sidelined Scott said Swallow would continue to do some off-field work with the team, with the club also considering sending him on some overseas leadership programs.

Earlier, the North Melbourne skipper posted an image online of his injured leg, post-surgery.

Friday night's game against Geelong will be the first Scott has coached without Swallow - who had played 106 consecutive games before his injury - in his team.

Scott said inside midfielders Levi Greenwood and Ben Jacobs headed Swallow's likely on-field replacements, but made it clear his captain was almost irreplaceable.

"He leads us by example on field, his contested ball has been outstanding this year," Scott said.

"I think he should be spoken about in All-Australian contention if we stopped playing right now, so we're going to have to replace that ball-winning ability inside and that's been really crucial for us."

Nick Bowen is a reporter with AFL Media. Follow on Twitter: @AFL_Nick