Western Bulldogs defender Lachie Young is expected to sign with North Melbourne, reports AFL.com's Callum Twomey.

The 21-year old has reportedly turned down a contract from the Bulldogs in favour of joining North, who are also set to acquire free agent Giant Aidan Corr to bolster their backline.

Young is likely to join the Roos under a little-known AFL rule - which states that if a player is offered a third year contract on the rookie list, they have the ability to refuse it, become a free agent and join their club of choice.

The Dogs reportedly allege they did offer Young a position on their primary list and will force a trade.

The older brother of Docker Hayden Young, Lachie was drafted to the Bulldogs with Pick 6 in the 2018 rookie draft.

The Roos are set for a big list turnover for 2021 after delisting 11 players at the end of the season.

Forward Ben Brown has also been put up for trade, attracting attention from other Melbourne clubs, while Shaun Higgins is likely to move to Geelong.