WEST Australian teenager Sydney Stack is closing in on winning Richmond's final available list spot following an impressive two-month trial at Punt Road.

AFL.com.au understands a decision to add the talented midfielder is imminent under new rules introduced ahead of 2019.

The Tigers hold one of nine remaining positions across the league, with clubs given the chance to fill vacancies prior to March 15 as part of the pre-season supplemental selection period.

Stack's game smarts and nous around stoppages have stood out since he was invited to train with the Tigers in early December after being overlooked in the NAB AFL Draft.

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Challenged prior to Christmas to increase his endurance, the 18-year-old proved he was up to the task at the club's Queensland training camp last month.

After carrying queries over his professionalism during last season, Stack has relished the opportunity to live with coach Damien Hardwick since arriving in Melbourne.

Stack bounced back to win All Australian honours from just three outings in the NAB AFL Under-18 Championships after being stood down for WA's first match for failing to meet training standards.

The Tigers have already taken advantage of the new rules, landing former St Kilda and Gold Coast forward Mav Weller in November.

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Former listed players Tom Campbell (North Melbourne), Keegan Brooksby (West Coast), Corey Wagner (Melbourne), Zac Clarke (Essendon) and Shane Mumford (GWS) were also snapped up.

While clubs can opt to hold over their remaining list spots until the mid-season draft, Carlton is set to use one of its three available positions on VFL star Michael Gibbons.

The dual JJ Liston Trophy winner was expected to have to wait until late February to learn his fate, however a decision could be fast-tracked following the shock retirement of Tomas Bugg last week.

With the Blues already carrying one extra spot following the rookie draft, Bugg's departure created a third vacancy following the season-ending ACL to co-captain Sam Docherty in December.

Dandenong Stingrays graduate Matthew Cottrell has joined Gibbons at the Blues and has turned heads with his running capacity, clocking a sub six-minute 2km time trial last month.

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Others to consider across the country include Mitch Grigg (Norwood), Jye Bolton (Claremont), Marlion Pickett (South Fremantle) and Jay Lockhart (Casey), while Lachie McDonnell (Dandenong) was interviewed by the Blues less than a week before the draft.

Melbourne, Greater Western Sydney and Gold Coast all have one list spot open but are tipped to wait until the mid-season draft, for which a date is yet to be determined.  

The Suns have identified the need for a ruckman to assist Jarrod Witts, with doubts over Tom Nicholls' body.

The Western Bulldogs were set to have one extra spot before re-structuring their list post-draft to upgrade Buku Khamis from a Category B rookie.

The move allows the Next Generation Academy product to be eligible for round one selection, with Category B rookies requiring promotion to the senior list to play AFL.

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Hawthorn is considering adding Box Hill-listed beanpole Ned Reeves to its list by placing the retired Will Langford on the 'inactive' list.

Sydney has the same opportunity with Kurt Tippett, who remains on the club's list despite his retirement.

The Hawks are also weighing up the chance to replace Tom Mitchell for 2019, should it deem his broken leg season-ending.

A decision to do so would open up a tenth berth across the league.

However, the sight of him walking up stairs without a moon boot last week, just 19 days post-surgery, will have provided optimism for a potential late-season return. 

North Melbourne could also lean on the same rules for Majak Daw after the defender suffered "very serious injuries" after a fall from the Bolte Bridge in December.