Rugby league great Ian Roberts wants NRL players to be aware of the risks involved with playing a sport that left him with permanent brain damage.
Roberts, who first revealed he had brain damage in 2014, was part of a new study that tested the effects of repeated concussions on 25 retired NRL players.
The study was published on Thursday, and revealed long-term impairments for the former players.
"To be told you have brain damage is really hard to hear," Roberts told BBC.
"I was fully aware there was something wrong with me, but to be told I had scarring on the brain was surprising. It's irreversible damage."
The NRL said it was "aware of the study" and "takes concussion seriously and is continuing to adopt international best practice in concussion management".
But Roberts says players need to be better informed of the risks they're taking by stepping onto the field.
"Players need to be aware so they can make their own, informed decision," he said.
"They need to know the consequences of repetitive concussions, because there's a price to pay."
Roberts played 194 first grade games in stints with South Sydney, Manly and North Queensland.
He also represented Australia 13 times and played 11 State of Origin games for NSW, before hanging up the boots and trying his hand at acting.
But his brain damage affected his acting as well.
"In the last five years I've noticed my recollection of things has slowed down and my memory isn't as sharp as it was," he said.
"I first realised it at rehearsals for plays because my ability to learn lines has deteriorated."
Concussion expert Dr Alan Pearce revealed how the study was conducted.
"The objective of the study was to look at how the players have fared 20 years after their last concussion in a competitive rugby game," Pearce said.
"When we compared them to the healthy group, who were matched for educational level, there were a number of differences.
"I would have expected the players to outperform the control in the learning of a novel task due to the way they have trained as athletes, but they really struggled in learning new material."