ST KILDA veteran Sean Dempster has announced his immediate retirement, citing concern over head knocks.
Dempster had most recently played in the JLT Community Series in pre-season, when he copped a bump to the head from Port Adelaide's Nathan Krakouer.
Having suffered several concussions and head knocks, Dempster said he elected to call time on his career.
"I copped a little head knock and given my history over my career of receiving quite a few head knocks I've decided that it's a risk that's too great for me, especially now that I've got a young family. It's more than just worrying about myself, it's what it means to my wife and my young daughter," Dempster told the club's website.
"For the last couple of weeks the club has given me some time to myself and some time to go and get some independent testing done, which I'm still going through at the moment and is an ongoing assessment.
"The testing had nothing to do with my want to retire; I know it's the best thing to do for me and my family."
Dempster was a father-son recruit at Sydney and went on to play 54 games for the Swans, including the 2005 premiership.
He was traded to St Kilda at the end of 2007, where he played a further 168 games, making a name for himself as a hard-nosed defender.
Dempster played in grand finals for St Kilda in both 2009 and 2010, while he earned All-Australian selection in 2012.
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