MELBOURNE, Australia (AP) — A leading concussion expert from the United States says players in high-level contact sports still are often fearful of sitting out games after head injuries because they might lose their positions on their teams.

Chris Nowinski, a Harvard graduate and former wrestler, is a co-director of the Center for the Study of Traumatic Encephalopathy at Boston University, otherwise known as the “Brain Bank.”

It is one of the leading research groups in the world on the effects concussions are having on athletes, highlighted by recent cases involving NFL players.

Nowinski, in Melbourne meeting with officials from the Australian Football League players association, says “there still has to be a culture change with the players … they still have that impression that their job or role might be at risk.”