Former Brisbane Lions coach and official AFL Legend Leigh Matthews rated it as "the most amazing thing I think I've ever seen in a game of footy".

It was 2002 at the MCG and Jonathan Brown, in a trademark that would define his career and, perhaps, bring it to a premature end, ran 40 metres back with the flight of the ball, headlong into an oncoming pack of players to mark.

It was that sort of crazy bravery that defined Brown, who retired on Monday after one concussion too many, sustained against Greater Western Sydney in round 13.

Brown was still feeling the effects of the knock late into last week and received strong medical advice against continuing his career, which spans 15 years, 256 games, three premierships, a Coleman medal and multiple All-Australian and best and fairest awards.

He would have played many more games if not for serious injuries. By 2011, his style of play began to catch up with him when he suffered two concussions, both of which required facial surgery.

"It's become evident I don't respond or bounce back like I used to from those hits," Brown admitted.

Brown was certain to retire at the end of this season if not for the latest knock. "It wasn't worth the risk of going out there and copping another head knock and jeopardising my future with my wife and kids."

He said he "did not want to dramatise" his doctor's advice. "I'm OK, I'm going to recover. I'm sure my symptoms will clear up pretty soon."

However, he admitted that the incident in round 13 had been a "wake-up call". "It’s the invisible injuries, the head injuries that no one can really predict, and that's more important than what's below the neck."

He paid tribute to his wife Kylie, heavily pregnant with his third child, quipping that "we might get to witness the labour as well if I keep talking for too long". Brown said she had suffered in the past few years as he "kept putting his head in the wrong spot".

Brown said he would remain at the club for the rest of the year in a non-playing capacity before deciding on his longer-term future.

"I was fortunate enough that I was a Lions supporter as a young fella, as my father Brian played for Fitzroy. My heart bled for the Lions from the very start, so it made it a lot easier to bleed for the cause … It's probably come at a price to my body, but I wouldn't change it for the world."

Matthews said, affectionately but bluntly, that Brown "would be an idiot" not to follow the medical advice he had received. Renowned for his own toughness on the field as a player, he described Brown's physical courage in very simple terms.

"Toughness is about keeping your eyes on the ball when you don't know where the pressure is coming from,'' he said.

"That running back with the flight of the ball was just a by-product of wanting the footy; [just] going at it and not caring who might be coming from another direction."