Greater understanding of the dangers of concussion could lead to more rugby players being urged to retire, according to former World Rugby medical adviser Dr Barry O'Driscoll.
Ireland fullback Rob Kearney suggested this week that players had become more honest as awareness of possible long-term effects increased.
On Wednesday, Matthew Pewtner, a Wales sevens specialist, was forced to quit the game, becoming the third Welsh professional in less than a year to do so following a concussion.
"We have moved on with our knowledge and we're more ready to advise players to retire," Dr O'Driscoll told the BBC. "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."
O'Driscoll -- who quit his role with World Rugby [then the IRB] in 2012 over their handling of concussion protocols -- also suggested that Wales wing George North could be one knock away from having to consider his own future.
North played on against England in the 2015 Six Nations despite taking two blows to the head, and having missed a 2014 autumn international because of a concussion.
Following a subsequent knock, the Northampton wing did take a break from the game and has since made a successful return to action, scoring a brilliant try in Wales' 27-23 defeat of Scotland last weekend.
"I'm sure if he [North] gets another one he will have to consider whether the worries about what the inference is from these is enough to make him give up the game," O'Driscoll said.
"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."