Constable has been kept to just 12 matches across his opening three seasons at Kardinia Park and has been a dominant force for the Cats' VFL side this season.
Despite averaging 35 disposals per game across his past five matches in the reserves, Constable hasn't been able to break into the senior side, with his last match coming in Round 3 as a medical sub.
The 22-year-old was understood to be considering a departure from the Cattery last year, however no real interest seemed to emerge.
However, according to SEN's Sam Edmund, should a keen rival pursue the tall midfielder he would stand a good chance to leave Geelong at season's end.
"Charlie Constable is the really interesting one and not for the first time,” Edmund told SEN.
“But the difference this time is he’s out of contract, the Cats want him to stay and they’ve told him they want to re-sign him... and there’s a seat for him in the future.
“He’s tearing up the VFL. He tried to orchestrate a trade last year with a year to run on his contract but no suitable offers emerged so he stayed.
“If an offer does come from a rival club, he’s out of there. He will take it and he’s there to be taken from a rival club’s point of view.
“Charlie Constable is a watch this space as the season unfolds.”
Constable is among a number of players at Geelong that remain unsigned past this season whilst facing a challenge to cement their place in Chris Scott's lineup.
Unlike Constable, both Clark and Narkle are interstate products, hailing from Western Australia.
Out-of-contract Geelong trio Bradley Close, Lachie Henderson and Gryan Miers are understood to be close to new deals, while the likes of Cameron Guthrie, Shaun Higgins and Rhys Stanley are yet to recommit.