The 22-year-old was one of four players who departed the club before the final game of the season; he was joined by Riley Grundy, Tobin Cox and Wylie Buzza.
Atley made his debut against West Coast in round 9, 2017 where he recorded 14 disposals.
Atley then played the next two games before not returning to the senior side until round 9, 2019 against the Gold Coast.
“We’ve reached the time of the year where we have to make difficult decisions about the direction we take with our playing list,” Power head of football Chris Davies said.
“I would like to thank Joe, Riley, Tobin and Wylie for their efforts and professionalism during their time at the club, and the contribution they have made to our group.
“They will always be part of the Port Adelaide family, and we wish them well for the future on and off the field.”
Despite showing consistent form in the SANFL in 2019 for Port Adelaide’s reserves’ side, Atley was unable to break into the senior side due to the Power’s strong midfield depth.
He finished equal-fifth with Sam Mayes in the reserves’ best and fairest last season.
Atley was drafted by the Power with the 34th pick in the AFL national draft after developing his game at the Bendigo Pioneers.
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