Other players prior to that who have retired early due to concussion include Heritier Lumumba, Jack Fitzpatrick and Justin Clarke. Another Saint, former No.1 draft pick Paddy McCartin, has also struggled throughout his career following several knocks. Stevens will finish his career on 91 AFL games, having played for West Coast and the Western Bulldogs prior to joining St Kilda. Koby Stevens in action in round one against the Lions. Concussion has forced his retirement. Credit:AAP It was in the Saints' season-opening game against the Brisbane Lions at Etihad Stadium that Stevens suffered his head clash.

He played six days later against North Melbourne in round two and it wasn’t until the build-up to round three that he told St Kilda officials about his problems. "I'd just come back into the side, so I obviously didn't want to speak up and we had a pretty big game that Friday against North Melbourne and I just went out and played," Stevens told Fox Footy in May. "It wasn't until that next week when I was really bad, I felt really ill. It wasn't great, I went into the doctors and [sought] some more advice after that. "I was pretty good in the early days, but we had a scan result come back that suggested that I did have changes to my brain. "I was pretty hurt as it was pretty tough to take. I've taken hits, come back from them strong, but to have someone say there's been changes to my brain and they can't really tell you what they are, they're just there, it's tough."

Stevens, who hasn’t been able to train at any level since round two, had also put his university studies on hold while continuing to deal with the lingering effects of his concussion. Taken at pick 23 by West Coast in the 2009 national draft, Stevens played 11 games for the Eagles before being traded to the Bulldogs. Stevens flourished at the Bulldogs, playing 63 games and kicking 32 goals, and had his breakout game in round nine of 2013 – ironically against St Kilda – where he had 31 disposals and booted three goals, picking up two Brownlow votes. Stevens was also unlucky in 2016, the year the Bulldogs stormed to their famous premiership. He played the first six games of the season, averaging 26 disposals, before being struck down by an abdominal injury that essentially forced him out of the next two months.