FORMER Fremantle ruck-forward Zac Clarke is one step closer to joining Essendon, with the AFL ruling him eligible to sign with the Bombers under new rookie rules.

AFL.com.au reported on Tuesday night that Clarke and Essendon were waiting on AFL approval to enable the 101-gamer, who played in the WAFL this year, to join the club and avoid the draft.

The rules mean any player who previously nominated for the draft or retired, delisted himself or was delisted and spent a year out of the AFL becomes a free agent of sorts.

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It is a similar arrangement that will allow Shane Mumford to come out of retirement and rejoin Greater Western Sydney without the risk of a rival team swooping in the draft.

They have the opportunity to sign as Category A rookies in the pre-season supplemental selection period between December 1 and March 15, after next week's drafts are over.

Clarke, 28, doesn't qualify as a delisted free agent because he spent a season out of the AFL, but the new rules are effectively an extension of that status.

Any player delisted in a previous year qualifies to sign with any club in the SSP, but teams cannot cut a footballer then re-recruit them via this method in the same year.

The only scenario where that could happen is if that player goes undrafted before the SSP.

That means clubs still risk losing a player when they delist them with a promise to re-rookie them.

What will likely become known as the Mumford rule allows the same luxury for a retired footballer and/or a player who delisted himself and has not been on an AFL list for at least one year.

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A player who retires cannot sign in the SSP in the same year unless they nominate and are overlooked in the drafts.

However, a player who nominated for and was not selected in the National Draft and committed for a further year as a 19-year-old in a Northern Academy or Next Generation Academy is not eligible for SSP selection.

Clarke chose the Bombers over at least two other clubs, both of which he had either undergone a medical or had organised to.

Essendon preferred the 203cm giant over Western Bulldogs discard Tom Campbell, who, like Clarke, completed a medical at Tullamarine.

The Bombers entered the mature-age ruck market after Matthew Leuenberger decided to retire despite having a one-year offer.

Clarke would give them an experienced back-up to Tom Bellchambers and allow 20-year-old Sam Draper to continue his development in the VFL without as much pressure to perform.

The Dockers cut Clarke at the end of the 2017 season after two surgeries and related complications with the patella in his left knee ruined his last year out west.

But he bounced back this past season to star with eventual WAFL premier Subiaco.

Clarke made 20 WAFL appearances and kicked 28 goals in the 2018 season, while averaging 15.7 disposals, 4.6 marks and 39 hit-outs.

He had at least 50 hit-outs in his last three matches this past season, including the Lions' Grand Final triumph over West Perth, and managed the feat twice more before that.