The SANFL was affected by the VFL expansion by players leaving their home state, and one team, Port Adelaide, attempting to join the VFL.
Port Adelaide attempted to join the VFL in 1990, though unsuccessful due legal disputes with the SANFL, thus forming the Adelaide Crows
Port Adelaide finally joined the AFL in 1997, becoming the second South Australian club to join the AFL, though they were forced to change their identity from the Magpies to the Power due to Collingwood already owning the licence to the Magpies.
Both teams found off field traction with their fans, due to the fans of the Port Adelaide SANFL team mostly keeping their alliance. Adelaide won their first premiership in their sixth season, and continued their success the next year, winning their second premiership,since then the crows have not played in another grand final. Port Adelaide only won one AFL grand final after joining, coming in 2004, stopping the Brisbane Lions from winning their fourth in a row.
The effects of the expansion of the VFL had less of an impact on the SANFL than that of the WAFL, with many players chosen to play in the VFL from South Australia, deciding to remain home and play for the teams they have followed since they were children.
Because of Port Adelaide's attempt to join the VFL, the SANFL began to lose traction, eventually deciding that the only way to keep South Australian football from becoming irrelevant in Australia and falling behind the rest of the country, that the Adelaide Crows would be formed to represent all the teams in the SANFL.