MELBOURNE, AUSTRALIA - AUGUST 13: Koby Stevens of the Saints and Angus Brayshaw of the Demons recover after a collision during the 2017 AFL round 21 match between the Melbourne Demons and the St Kilda Saints at the Melbourne Cricket Ground on August 13, 2017 in Melbourne, Australia. (Photo by Michael Willson/AFL Media/Getty Images)

St Kilda midfielder Koby Stevens has opened up on his extensive battles with concussion that have ended his 2018 season, and potentially his AFL career.

The former Western Bulldog told Fox Footy’s On The Mark yesterday that recent scans had shown the heavy knocks he had copped early in the season had caused changes to his brain.

Stevens said he suffered a head knock in round one but didn’t was to lose his spot in the side so he played the following week, despite still suffering concussion symptoms.

“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,” he said.

“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 seeked 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.”

While the 26-year-old hasn’t been able to play footy, he has still been spending some time at RSEA Park until last week when him and the club decided to rule out for this season.

“It’s a day-to-day thing. Some days I wake up and I’m pretty clear and then I try to do a little bit of exercise and as soon as my heart-rate gets up, I just get real chronic headache and pretty dizzy,” he said.

“I haven’t run or touched a footy in eight weeks, so it’s been pretty difficult and frustrating.”

This isn’t Stevens first year of battling head-knock related concussion issues.

In round 21 last year he clashed with fellow concussion sufferer Angus Brayshaw of Melbourne, and the Saint says that was his worst hit yet.

“I reckon that one was the worst one I’ve ever had,” he said.

“I wasn’t knocked out, but it felt like a bomb had gone off.

“I couldn’t hear anything, and it hit me right in the ear drum, so for about 10 to 15 minutes I had ringing in my ears.

“I quickly ran off after that but then something happened on the field. There was a quick sub that had to be made, so I just ran back out, but I had no balance.

“I was leaning to one side where I’d been hit and was about to fall over, so I knew something was pretty bad then.”

Stevens has also differed his university course due to the dizziness, headaches and an inability to concentrate for long periods of time.