Roy Keane believes footballers who are concerned by the risk of injury would be better off playing chess.
Former Republic of Ireland international Kevin Doyle announced his retirement last week, having grown concerned during his time with Colorado Rapids about the long-term damage from concussions.
But Keane believes footballers' attitudes should reflect those in rugby - the Ireland assistant coach urging players to accept the dangers of sport.
"I suppose there is research ongoing with regard to concussion," Keane said. "If you're worried about the physical side of any sport, then play chess. It's part of the game, whether it's hurling or American football.
"You see the rugby lads. When you cross the line, there is an element of risk involved. They all want to play but know the risk. I'm sure there is research. But there is a chance you might get hurt. It is part of the game.
"I was surprised when I read about [Doyle's retirement]. He was involved in provisional squads. It's sad, he feels he made the right decisions.
Statement on my retirment pic.twitter.com/3dTXdk4EXU-- Kevin Doyle (@KevinDoyle1983) September 28, 2017
"He's a decent guy and did well for Ireland. He's 34, felt he had a decent innings and maybe this is the right time. Health is your wealth as they say.
"I saw the statement which said he had one or two concussions. We mentioned risk and, when you walk on to a football pitch, there is an element of risk. He feels it is right for him.
"It is part of the game, players picking up injuries. He is a centre forward and he gets a few knocks from centre-backs; I'm sure he has given out a few himself. It's a physical game."