St Kilda want Geelong's first-round draft pick, at number 14, and a player in any trade for the contracted ruckman, who is about to turn 31. The Saints failed to agree a deal for Marshall to move to Geelong 12 months ago, when Tom De Koning arrived at the Cats, but are now driving a steep asking price.
The Saints have not nominated a player they would like to pair with the pick, having earlier made a failed bid for Lawson Humphries.
Saints football boss Lenny Hayes told Trade Radio last week it was "going to take a little bit to get to a point where we're satisfied as a football club because of how highly we rate Rowan," but said the club was open to further discussions.
Such a deal would exceed recent transactions involving ruckmen, including Brodie Grundy's trades to Melbourne and Sydney, although his deal involved the sharing of his contract. Adelaide's Jordan Dawson cost the Crows pick 14 when he was traded from Sydney in 2022, but the Saints can drive the asking price for a contracted player.
Meanwhile, Gryan Miers' future remains cloudy after he took the precaution of doing a medical with West Coast before leaving for Italy. Miers is contracted for two more years and is reportedly happy at the Cats. He did the medical as a safeguard should talks between West Coast and Geelong lead to the Cats being open, or keen, for him to move.
Elsewhere, Ben King is expected to become a Hawthorn player by the end of the trade period.