It was the shock move of the 2023 AFLW trade period.

Unbeknownst to the football public, Melbourne premiership defender Libby Birch was at a juncture in her career, and had a number of keen suitors.

Hawthorn was among the interested sides, keen to add some experience to its young group.

Then only a few days after a Grand Final loss, with a side already packed with stars, North Melbourne pounced.

Senior coach Darren Crocker and list manager Flynn Loft had less than 24 hours to quickly move on from their disappointing defeat, and met with Birch, eager to add some height and her intercepting ability to their backline.

The Roos' notoriously disciplined system-based defence – and the chance for further premiership success – appealed to the tenacious competitor.

"I had been given an amazing opportunity at the Dees after coming across from the Western Bulldogs, to come to a side with my best mate Daisy Pearce and play with her again, and to play with some players I had played with at Darebin Falcons," Birch told AFL.com.au.

"I was really excited about the potential of a new journey, and from the bottom of my heart, I saw some incredible chances at North Melbourne to have a real impact and be part of a side that was again chasing premiership glory.

"But number one, it was how do I get better as a player? I've been in the system for eight years now, and I wanted to grow as a player, as a person and as a leader again, and this new challenge, being uncomfortable again, has almost reinvigorated my career.

"One of the things that really excited me was the fact I could train against Tahlia Randall, Kate Shierlaw and Emma King, who I've had some fierce battles with in the past. I've loved the fact I could train against them the entire pre-season. There's no doubt the AFLW is absolutely flying. It's getting better and better, and you need to individually lift as a player."

Time and again in the interview, Birch refers to playing in the backline. It's a vital part of her identity as a footballer, and works perfectly with her character, fiercely determined and diligent.

"I first learned the game at 18 from (former Melbourne strategist) Jane Lange, she said to sit myself in the backline and follow someone around, as that would be the easiest way to learn the game," Birch said.

"From that moment, I've just tried to master my craft in the backline, in whatever team I'm playing in, and be a better player each time I step on the field. I love it because it's tough, you have to be gritty, and you have to work with your teammates.

"It's not a position that's spunky, or you get to celebrate often, and I love that behind-the-scenes humbleness that backliners are, and that sort of personifies me."

Birch, a qualified physiotherapist, ruptured her medial cruciate ligament in her left knee at training just under six weeks before round one.

Traditionally a 6-8 week injury, she recovered in time to play against Brisbane in the first match.

"It was originally almost diagnosed as an ACL (anterior cruciate ligament), so for a few hours there before I got the scans, I felt like I'd let everyone down. I'd come to the club, and injured my ACL and I'd be out for 12 months," she said.

"But then I got the scan result back and it was like 'Shit yeah, how good is this, an MCL?'. The support staff and physios, we did an amazing job working as a team to halve that recovery time and get back to full training within four weeks.

"The first two weeks, I was in a brace, so there wasn't much I could do other than keep my muscle strength up in that leg. But almost the most valuable aspect of being injured was actually watching the game plan and my teammates from the sidelines, I got to stand out of it and watch what their strengths are. 

"So it was a lot of time visualising and intently studying training. I know that sounds a little strange, but it was almost like I was physically training while I wasn't."

When the Roos meet the Demons on Sunday it won't be the first time Birch has come up against a former side, having come up against the Western Bulldogs while in Melbourne colours.

"Playing at Springfield in round one, the first thing I thought about while stepping on that field was the fact I won a premiership there with my Melbourne teammates," she said.

"It's a challenge from the emotional side of things, going back to a place where you trained, played and shared so many memories with former teammates, but it's about how you handle it and embrace it. 

"I love playing at Casey, I love the fact I've played on a lot of players from that team and understand how the Dees work, so I'm trying to use all that positive energy to crack in with my team, who are in a really good position to take our system-based game plan to the Dees."