Koby Stevens has retired.

The St Kilda midfielder, 27, is battling persistent problems with concussion.

He told his teammates on Monday his career was over.

“This decision has taken me a long time to come to,” Stevens said in a statement published by the Saints.

“Football has been a huge part of my life for as long as I can remember, and I do recognise how lucky I have been to play professionally for the past nine years.

“However, after lengthy consultations with my family and on the advice of doctors, I’ve made the extremely hard decision that I cannot risk my health and future for the game.

“I’m so grateful for the support of the entire St Kilda Football Club, particularly the medical and player development staff who have been extremely supportive of me over the past few months.

“To my teammates and coaches, both here at the Saints and at my previous clubs, thank you for allowing me to live my dream. I can’t thank you enough for all that you’ve done.

“Lastly, to my friends and family I couldn’t have done this without you.”

Stevens last played for the Saints in round 2.

The midfielder also spent time at West Coast and the Western Bulldogs.

He played 91 games at the highest level.