Jackson played six games in his first season before suffering a hamstring injury at training on the Gold Coast and he did not play after round 11, while Brown has played 75 games in nine seasons at Geelong, Essendon and Melbourne.
The Demons’ two other picks from the 2019 AFL national draft, Pickett and Trent Rivers, had already signed contract extensions beyond 2020.
After not receiving serious offers during the trade period, Tom McDonald remains at the Demons where he is contracted until 2022 and is expected to adopt a different program to give him options to play up the ground or in defence.
Having spent the past two seasons outside the eight, the club is under pressure to make the finals in 2021 with the CEO Gary Pert restructuring the football department after a review. Alan Richardson will be the football manager responsible for performance while Josh Mahoney becomes responsible for facilities and administration.