Medical expert O'Driscoll voices concussion fears
Former World Rugby medical adviser Dr Barry O'Driscoll has outlined how an increasing number of rugby players may have to retire due to increased awareness of concussion.
And Dr O'Driscoll, former Ireland captain Brian O'Driscoll's uncle, also believes that players who suffer three or more concussions should "seriously think about their future".
Ireland out-half Jonathan Sexton has sustained four concussions and, although his last three injuries were not concussive - whiplash, neck and a "bang to the head" which did not lead to concussion - there is growing concern about the player's welfare.
Former Ireland captains Brian O'Driscoll and Keith Wood have encouraged the player to alter his tackling technique while another, Donal Lenihan, suggested that a "serious call" needed to be made about his well-being.
However, Sexton, who has been injured in three successive games, has shrugged off any lingering concerns about the issue.
Earlier this month, he said: "We see the best neurologists and they tell us if we're going to play or not based on tests done by the best specialists."
But Dr O'Driscoll has admitted that the increased awareness of the frightening consequences of concussion may begin to force the hands of medical experts.
"We have moved on with our knowledge and we're more ready to advise players to retire," he said. "Every case of this saddens you and worries you just that little bit more.
"It does seem that with the much bigger impacts and speed of the game that these repeated sub-concussive and concussive knocks are becoming more damaging more frequently.
"It's a balance for each person to make and I don't think we're anywhere near the stage of the game of saying 'no, that's it, we can't pick you anymore', (because) we don't know enough yet. But any player at all who has had three or four concussions, in my opinion must seriously think about the future."
Dr O'Driscoll - who has previously criticised rugby's concussion protocols - said the handling of players like George North who have suffered multiple blows is a particular concern.
He added: "If he gets another he will have to consider whether the worries is enough to make him give up the game."