Hartlett played 193 games for the Power after debuting in 2009. The halfback is was a part of the leadership group in 2021 after serving as vice-captain in 2016, 2019 and 2020.
The 31-year-old has said publicly that he would like to play on in 2022 despite being told by Power coach Ken Hinkley that his body wasn't able to sustain the level required for AFL football.
List manager Jason Cripps thanked Hartlett for his years of service.
Hamish has been a much-loved character at the club for a long time and it is difficult to say farewell,” Cripps said.
“He has shown incredible resilience to come back from a number of injuries, most notably a serious knee injury in 2018, and has always put the team first.
“Hamish has been a key leader in our football group, always willing to share his experience and to support the development of our younger players.
“It is because of the need to continue to develop our group that we make the tough call regarding Hamish’s future at the club and we wish him well in football and in life.”
Garner managed four games for the Power. Cripps acknowledged that Garner may not have been given as much opportunity as he would have liked due to the depth in his position at the club.
“Joel has become a victim of the depth we have in our backline, which has made it hard for him to get opportunities at AFL level,” said Cripps
“He has been a player that has given everything he has to our club, often providing important leadership to a young and inexperienced SANFL team.
“With our season coming to an end we have made the decision to part ways with Joel and allow him to focus on what is next in his career. We wish him every success with that next step and thank him for his dedication over the past four seasons.”