NORTH Melbourne recruit Libby Birch will miss more than a month of preseason after scans confirmed a MCL injury on Tuesday.

Birch, who joined the Roos via trade from Melbourne during December's player movement period, will miss at least six weeks of pre-season as she recovers from the injury. This period will include the officially sanctioned practice matches to take place over August 17 and 18.

"This is obviously disappointing news for Libby, especially so close to the start of the AFLW season," North Melbourne women's footy manager Erin Lorenzini said.

"A two-time All-Australian defender, Libby was an important addition for us during last year's trade period and has already made an impact both on and off the field over the pre-season. She is expected to be sidelined for at least six weeks, but we will have a better understanding of her return to play timeline as we monitor her rehab progress."

The key defender is the only player in AFLW history to win a premiership at two different clubs – Western Bulldogs in 2018, and Melbourne in 2022 (S7) – and joined the Roos after last year's Grand Final appearance.

She has played every possible game since debuting in round one, 2017 with the Bulldogs, amassing 77 career games across her eight seasons. In that time, she has been named All-Australian twice – 2020 and 2022 (S6).