ADELAIDE defender Matthew Jaensch has retired from the AFL, effective immediately.

In a move that teammate Rory Sloane told was tough to understand, Jaensch said he lost his passion for the game as he continued his recovery from a knee reconstruction.

The 26-year-old played 74 games for the Crows after beginning his career as a rookie in 2010 and developed into a damaging half-back flanker before injuring his knee.

"Playing in the AFL takes a great deal of focus and commitment and right now I’ve lost my passion to play the game I grew up loving," Jaensch said.

"I would like to thank the club for the opportunity to be in the AFL for seven years and I am very proud to have played at the highest level, and feel really privileged to have taken the field with some of the superstars of the game.

"I would finally like to thank my teammates for their support and fun times shared, I wish them all the success for the coming season.

"I look forward to pursuing a new chapter of my life."

Speaking on's First Bounce, Sloane said the popular defender pulling the pin on his career was tough to understand.

"It's a strange circumstance. It's hard to comprehend a guy losing the love for the game he grows up playing," Sloane said.

"We just feel for Matty at the moment and we're there to help and support him at the moment.

"His injury's gone pretty well, but as he mentioned he's at the moment not ready to cope with the demands that AFL football has on us."

Adelaide's head of football David Noble thanked Jaensch for his effort.

"Matthew has had to contend with a number of difficult events in recent times, including his recovery from a serious injury," Noble said.

"He is a talented footballer and we wish him the very best and will provide him with ongoing support as he transitions into the next phase of his life."

Jaensch made a name for himself in the West Lakes changeroom as one of the club's best practical jokers.

Among Jaensch's joke CV was a stunt from a number of years ago, when he parked then-teammate Kurt Tippett's car in a 15-minute zone and allowed it to accumulate tickets throughout the day.