The AFL's coronavirus protocols will prevent Port Adelaide fielding a side in the South Australian state league for the first time in 150 years.
Port Adelaide and the Adelaide Crows won't field teams in the SANFL this season after the AFL ruled AFL-listed players can't play in state leagues.
Both Port and the Crows have had effectively reserves sides compete in the SANFL in recent years.
Port's SANFL team, nicknamed the Magpies, is a foundation club of the state league.
"It is very disappointing to not have Port Adelaide participate in the SANFL competition this season, especially given it is our 150th anniversary," Port chief executive Keith Thomas said on Tuesday.
"However the AFL have made it clear that for health and safety reasons we need to restrict the number of people our players interact with and competing in another competition opens that up significantly.
"The Magpies are an integral fabric of our football club and we will do everything in our power to ensure we return to the status quo in 2021."
Port Magpies were beaten in last year's SANFL grand final by Glenelg, who downed the Crows in the preliminary final.
SANFL chief executive Jake Parkinson said it was disappointing for the state league to lose the two AFL clubs for the season.
The SANFL, like the AFL, has suspended competition because of the coronavirus with a return date yet to be decided.
Australian Associated Press