A former Essendon key forward has been tipped as the leading name among Collingwood's crop of Supplemental Selection Period hopefuls.

After a year with the Magpies' VFL side, ex-Bomber Joshua Eyre has emerged as a likely new addition to Collingwood's senior list after trialling as a key defender.

Eyre, who is one of three former AFL-listed players training at Olympic Park, pushed for a list spot at St Kilda last pre-season before falling short to duo Liam Stocker and Anthony Caminiti.

The forward-turned-defender has been among the top train-on prospects under Craig McRae this summer as the Magpies look to find their next Oleg Markov.

With three list spots open for the season ahead, the reigning premiers have had six SSP figures take part in their pre-season program since December.

Eyre is joined by former St Kilda midfielder Jack Bytel, ex-Port Adelaide tall Brynn Teakle, local footballer Sam Sofronidis, VFL star Lachie Sullivan and Collingwood VFL captain Campbell Hustwaite in competing for a list spot ahead of the February 19 signing deadline.

Across match simulation, as well as fitness and drills sessions, Eyre is seen to be among the most promising of Collingwood's train-on contingent, with the 21-year-old "in the box seat" for a second chance in the AFL.

"I think Josh Eyre is in the box seat to get the spot," AFL.com.au reporter Josh Gabelich told AFL Daily on Tuesday.

"He was part of the program last year in the VFL. Lachie Sullivan dominated in match practice last Friday.

"It's a really healthy competition. I think it's going to go down to the wire."

St Kilda trialist Josh Eyre (Image via St Kilda FC)

Eyre would add to Collingwood's key defensive stocks that faced uncertainty over the future of premiership backman Nathan Murphy prior to his recent concussion panel clearance.

The Magpies' stopper has been given the all-clear to continue his career after suffering his 10th concussion during last year's grand final.

Collingwood also have uncapped backman Charlie Dean among their depth options to support skipper Darcy Moore on the last line.

Sofronidis shapes as a smaller-sized intercepting defender, while Teakle has shown an ability to play a key position role across all three lines of the field.

Bytel, Sullivan and Hustwaite might all be seen as viable Taylor Adams replacements after the veteran midfielder departed for Sydney over the recent off-season.

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Collingwood is anticipated to hold at least one spot open while keeping injured key forward Dan McStay off the inactive list, meaning two SSP additions are likely.

AFL clubs have until February 15 to have SSP talent training in their program, with the signing deadline to come four days later.

Richmond and Fremantle also have train-on players listed just over a week out from the deadline, while North Melbourne and Gold Coast look unlikely to fill list vacancies and will instead hold over their spots for the Mid-Season Draft.