North Melbourne has kept one of its best young leaders out of next year's free agency pool, re-signing Jamie Macmillan until the end of 2019.

Macmillan was due to come out of contract at the end of next season but the wingman/defender agreed to a new two-year deal with North this week.

At 24, Macmillan is the youngest member of the Roos' leadership group and, although vice-captain Jack Ziebell is the odds-on favourite to replace Andrew Swallow when he steps down as captain, the former Oakleigh Charger will also be in the frame.

Macmillan said on Thursday he was pleasantly surprised when North approached him so early about a contract extension and had not hesitated to turn his back on free agency.

"I'm really happy with where the club's at and how I've fitted in here and how I enjoy life at North Melbourne, so [free agency] didn't really cross my mind," Macmillan said.

Macmillan's elevation into North's leadership group last season might have surprised some outside Arden Street, but the former Scotch College student has long been lauded internally for his leadership skills, on and off the field.

His main strength as a leader, he says, is his ability to direct teammates during games.

"I think for me it's just the ability to identify things on field and understanding the game, helping other guys out with their structures," Macmillan says.

"That's probably what, in a sense, got me in the leadership group, but now I'm learning more about the off-field side of things and the ability to identify things we can improve around the club, and building a really strong culture which we're really proud of.

"So that's something that I'm working really hard on."

As a player, Macmillan, pick No.37 in the 2009 draft, has become increasingly important to North.

When fit, he has been an automatic senior selection since 2012, playing mainly in defence and on the wing.

This year, he has predominantly started on the wing, but then worked back hard to help out North's defence as a spare man.

His ability to intercept opposition forward-50 entries has been vital, especially when North's backline has been without Lachlan Hansen's intercept marking for two of the first three rounds.

Macmillan has high hopes for what North can achieve in the four years before he next comes out of contract.

"Hopefully in the next four years we can win four premierships, that's the plan," he says.

"There's a lot of work ahead of us, but I'd love to have some more success in the next 2-4 years, for sure.

"We've made two 'prelims' the last couple of years. While it's fantastic and a great experience to play in those prelims, you always want to go and play the one game more and win that game.

"That's the plan for this year, certainly, and then going forward as well."

Inevitably, North will lose some of its best players to retirement over the next four years.

They could include spearheads Drew Petrie and Jarrad Waite, both 33, class ball-users Daniel Wells, 31, and Nick Dal Santo, 32, and versatile defender Michael Firrito, 32.

Even football's Peter Pan, Brent Harvey, 37, will eventually 'grow up' and retire.

Macmillan is confident, however, that these veterans' impending retirements won't leave North's list in a state of transition, where it has to take a few steps back before going forward.

"That's what's been said but I certainly don't believe that. I think that's one of the exciting things that we see a lot of guys that are young guys coming through and on the weekend a couple of the first-year players were exceptional (in the VFL)," Macmillan says.

"So we've got real confidence that when guys come out [we'll be OK]. For instance, when Boomer retires he's been teaching all those other young guys all of his tricks of the trade, so they've learned off him and they'll come in and play a role.

"At this footy club, we're really big on that and just making sure that we've got 22 contributors each week.

"No footy club is ever going to win a premiership if they're just relying on one or two guys.

"I think we're in good stead."