Kolodjashnij was the player who signed a secret waiver in his Geelong contract in 2024, requiring him to take all legal responsibility for future brain trauma so he could keep playing at the club.
The Cats were last month fined $140,000 for failing to officially let the AFL know about the concussion waiver in Kolodjashnij's contract - $100,000 plus a suspended sanction of $40,000 from last October, stemming from a league investigation into the club's third-party agreements.
After news broke in early August that the Cats had struck a secret deal with a player with a history of concussion, Kolodjashnij identified himself as the player involved.
Kolodjashnij, 31, had played AFL and VFL for the Cats earlier in the year but didn't feature at any level after the concussion scandal emerged.
The versatile defender played 11 AFL games this season, taking his career tally to 209, which includes the 2022 premiership.
"I am so grateful for the many fond relationships and memories the Geelong Football Club has provided me," Kolodjashnij said in a statement.
"Football has been such a significant part of my life.
"I feel lucky to have shared it with some of my closest friends, and to have had the on-field success that we had during my time at the club."
Kolodjashnij's twin brother Kade, who played for Gold Coast and Melbourne, also retired due to concussions
Geelong football boss Andrew Mackie paid tribute to the popular defender, who was a mainstay in the Cats' backline between 2015 and 2024.
"Jake's contribution to our football club extends far beyond his impact on the field," Mackie said in a statement.
"He earned enormous respect through the way he approached his football, the care he showed for his teammates and his unwavering team-first attitude.
"Jake built a reputation as one of the competition's most reliable defenders, his coaches and teammates had complete confidence he would take on whatever role was required and get the job done.
"His career has been defined by consistency, resilience and selflessness. The determination and professionalism he displayed throughout his journey are qualities that made him such a valued teammate and person within our football club."
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