Sellar was delisted by the Demons after 23 games in two seasons, but he is committed to eventually returning to the elite level.
The 24-year-old drew interest from SANFL and VFL clubs, but his decision to move to the Western Australia was driven by his girlfriend's university education.
South Fremantle, East Fremantle and Perth are locked in negotiations to secure the 196cm defender, who was recruited with pick No.14 in the 2006 NAB AFL Draft and played a total of 44 games.
After playing as a defender and back-up ruckman with Adelaide, Sellar moved to the Demons after five seasons and was used purely in his preferred position as a tall defender.
He was down the pecking order in the backline however, with James Frawley, Colin Garland and Tom McDonald all preferred in the key positions.
Sellar is pursuing a career outside of football in commercial real estate but wanted to play at the most competitive level he could in 2014 to keep his AFL hopes alive.
Twitter: @AFL_Nathan
