Motlop, 19, played three games for the Power in the middle of the season and also managed a handful of appearances for SANFL side North Adelaide before succumbing to the injury.
He has been placed on the club’s long-term injury list, but development officer Stuart Cochrane said he expected the skilful half-back to be ready for the start of pre-season training.
"The injury had been hampering him for a while. It was good he was still able to play some senior footy, but we decided it was best to give him a rest and get him right for next year," Cochrane told portadelaidefc.com.au.
"Marlon probably didn’t know himself that he was having issues. He thought he was just tightening up, but there were signs there that the club has been managing.
"Unfortunately, it got to a stage where he couldn’t run out games and wasn’t able to play with the same spark he showed over pre-season and earlier in the year."
Motlop, who is the cousin of star forward Daniel, was selected with pick number 28 in the 2007 NAB AFL Draft and has played a total of five AFL games.
Port Adelaide’s decision to place Motlop on the long-term injury list means the club has the option of elevating a rookie for the remaining rounds of the season.
