Carlton have handed former Melbourne defender Oscar McDonald an AFL lifeline, signing the 24-year-old via the Supplementary Selection Period.

McDonald will join the Blues as a Rookie for the 2021 season, edging out former Magpie and Crow Ben Crocker, delisted forward Callum Moore and Murray Bushrangers product Zavier Maher for the final list spot at Ikon Park.

The signing follows an impressive performance in Calrton's AAMI Community Series match against St Kilda last Thursday, with McDonald lining up as a forward before moving back late into the game.

McDonald finished his dress rehearsal with 13 possessions, six marks and three tackles as well as two hit-outs during a short spell in the ruck.

“Oscar has fit in really well with our backline group over the pre-season and we look forward to seeing him continue to strengthen those connections as the year evolves,” Carlton list manager Nick Austin said, per the club website.

“As we also saw on Thursday night, Oscar is also able to play other roles across the ground which gives us some flexibility across the board.

“It is never an easy situation for a train-on player however from the moment Oscar walked into the football club late last year he has done everything possible to earn a spot on the list. He already has six years of experience at the elite level, has a great work ethic and above all is a great person who will be a welcome addition to the playing group.”

The former Melbourne tall played 81 games in the blue and red, making his debut with the Demons in 2015.

McDonald will be in line to play for the Blues in their season-opener against Richmond next week, with Carlton set to be without star recruit Zac Williams following the MRO's verdict to hand the midfielder a one-game ban for his hit on Saints gun Hunter Clark.