Petty will go under the knife today to release the bleeding from his calf muscle, which will see him miss the opening rounds of the 2022 AFL season.
In a reversal of roles, the premiership defender will likely be replaced by Adam Tomlinson, who Petty usurped in the side after Tomlinson went down with an ACL injury in Round 7 of last season.
Despite Petty's untimely injury, the reigning premiers will head into their March 16 grand final rematch against the Western Bulldogs with a relatively healthy list.
The key defender played a pivotal role in the back six last season in delivering the Demons their first premiership in 57 years, playing 19 games in 2021.
Petty was drafted with pick 37 by the Demons in the 2017 AFL draft, and has played 30 games since.
The 197cm utility signed a new contract at the end of last season, extending his stay at Gosch's Paddock until the end of the 2025 season, which is exciting news for himself and the wider Demons community.
Melbourne are set to face North Melbourne and Carlton in pre-season clashes across the course of the next month before their premiership defence officially commences on the familiar turf of the Melbourne Cricket Ground.