When his right knee buckled beneath him during a January training session, Jackson Archer's immediate reaction was denial.

"When I first felt something go, I knew something bad had happened, but I just didn't want it to be the ACL," he says.

"And then when I found out the news, the feeling was just numb. Knowing I wouldn't be able to play all season was pretty frustrating. I just felt empty."

Two months on, rehab is well underway for the 23-year-old, who this week signed a two-year contract extension, keeping him at North Melbourne until at least the end of 2028.

When NMFC Media catches up with Archer, he's just completed a gym session, slowly rebuilding the quad strength in his injured right leg.

Earlier in the day, a small milestone: his first swim since the knee surgery.

"Obviously it's been a frustrating couple of months, not being able to do too much because I always like to stay active," Archer says. 

"But the support from everyone has been amazing. It's made the process a lot easier."

When the injury happened, Archer's teammates reached out immediately. His fellow defenders pitched in to buy him a lego set - a 9000-piece replica of the Titanic. It kept him busy and his mind occupied in the earliest days of rehab.

"The boys picked me up pretty quickly after the injury," Archer says. "The physio staff at the club have been really supportive and diligent too, and (club doctor) Kendall (Brooks)."

Veteran defender Luke McDonald, a long-term mentor, ensured Archer stayed involved in day-to-day activities at the club, from analysing training vision to match preparation as the season approached.

"He's been massive," Archer says.

He also received everyday support from housemates Charlie Comben and George Wardlaw, and his pilates instructor partner Sophie, who filled up countless 'Game Ready' ice machines and has been "amazing".

"So I've come to terms with the injury, and I'm just trying to get to work now," Archer says. 

"Put my best foot forward for hopefully a big pre-season."

A born competitor, Archer is no stranger to frustration. Injuries and suspension have restricted him to just 26 games in his first five seasons at North Melbourne.

In a sign of how highly he is rated at Arden St for his work rate and selfless professionalism, he was voted into the Kangaroos' emerging leaders group ahead of this season - his elevation into the role coming after his ACL injury.

"After doing my knee and knowing I wouldn't be playing, a big focus for me has been helping some of the younger boys," he says.

Among the players he is working with closely are new arrivals Hugo Mikunda and Blake Thredgold, plus forward-turned-defender Cooper Harvey and fellow father-son River Stevens - two players Archer has known nearly all his life. 

"I'm definitely keen to help them get the best out of themselves, whether that's on the field or off the field," he says.

"Anything from sitting down with them to go through match vision, to working on motivation, to taking them to recovery sessions.

"I feel like they're a young group I can connect with."

Watching from the sidelines during Round 1's win over Port Adelaide was a strange experience, knowing he won't play an on-field role in the season ahead, but Archer liked what he saw. 

"It was the most mature performance we've had since I've been at the club.  

"We controlled the game for four quarters, which is a massive step in the right direction."

Comben and McDonald were among the standouts for Archer, for their composed games at the heart of a co-ordinated Kangaroos backline, while new signing Tom Blamires ("he's such a team man", Archer says) looked immediately at home. 

"I'm actually excited just to watch the boys this year," Archer says. "I'll be a fan again, pretty much."

More than most players, Archer knows what it is to barrack for the Roos, having grown up around Arden St thanks to his decorated father, Glenn.

He says his contract extension reinforces what he's known his whole life - that he belongs in blue and white stripes.

"This place is like home to me. Has been ever since I walked through the door," he says.

"I'm just really, really grateful for the club to back me in with the new contract. It gives me a lot of confidence. 

"I'm so motivated to pay back that faith and be a part of this group going forward."

More gym sessions lie ahead, as Archer continues a rehab phase focused on gradually regaining his lost leg muscle following surgery.

"Spending a lot of time in the pool seems to help," he says.

"Then it's about ticking off those strength markers, and hopefully be running again in a couple of months. That's the goal."