Carlton are set to invite axed St Kilda defender Jonathon Marsh as a train-on player early next year as the club looks to fill it's one remaining list spot for the 2021 season.

According to's Mitch Cleary, Marsh is in line to join the Blues in hope of an AFL lifeline after being one of nine players cut from the Saints this off-season.

The Blues are also considering handing delisted Melbourne tall Oscar McDonald a train-on position, with the 24-year-old seen as one of the top prospects without a club for next season.

Carlton passed on an available rookie selection this week and will have the option to add to their list for 2021 via the Pre-Season Supplemental Selection Period.

The SSP will begin on January 6, with uncontracted players able to join squads from that date until March 9.

North Melbourne, Essendon, Sydney and Port Adelaide join the Blues in having one selection available for next year, while Melbourne, Richmond and Collingwood have two remaining spots and the Saints have three.

Adelaide are likely to move on Bryce Gibbs to the inactive list for administrative reasons after selecting him in the Rookie Draft, which would give them one spot to add to their squad.

Clubs are available to hold off on selecting players via the SSP and could look towards the Mid-Season Rookie Draft instead.