GEELONG defender Cam Guthrie is set to turn his back on free agency and sign a fresh three-year-deal with the club.

AFL.com.au understands the 25-year-old is poised to extend his stay at the Cats until the end of 2021 after fruitful negotiations ramped up in recent weeks.

His looming signature will follow the lead of 27-year-old Mark Blicavs in re-committing to the club for five years last month.

Both are seen as important pillars in Geelong's sustained success, part of the next wave after senior players Joel Selwood (30), Tom Hawkins (29), Harry Taylor (32) and Gary Ablett (34).

Guthrie has played the past fortnight in the VFL and is in the frame to return after the bye in round 15, having not played in the AFL since suffering an ankle injury in round three.

A restricted free agent, Guthrie has played 131 games for Geelong since debuting in 2011.

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Meanwhile, it is believed brother Zach Guthrie is closing in on a two-year extension to remain a Cat until the end of 2020.

The 19-year-old will be elevated off the rookie list at season's end after playing seven games to date this season.

Debuting in round 15 last year, Guthrie played nine games in his first season, including two finals.  

Fellow rookies Jamaine Jones and Jack Henry are also set to be re-signed before season's end, in a show of faith in the club's youngsters.

It comes after Lachie Fogarty, Charlie Constable and Mark O'Connor recently put pen to paper on extensions.  

Other out-of-contract players at GMHBA Stadium include Rhys Stanley, Jackson Thurlow and unrestricted free agents Daniel Menzel and George Horlin-Smith.