Wales full-back Leigh Halfpenny could be forced to retire unless he changes his tackling technique according to former dual code fly-half Jonathan Davies.
Halfpenny, 26, is being treated for concussion after suffering an injury in Wales' 61-20 win in Italy.
Samuela Vunisa caught his head with his knee as the Welshman tackled.
"If he gets more and more bumps on the head, there is a danger that it's career threatening," said Davies.
The Toulon player was taken off the pitch immediately, six minutes before half-time.
BBC rugby commentator Eddie Butler said in the Observer that Halfpenny's head would have been more protected had he tackled Vunisa leading with his left shoulder.
Davies, who won 37 caps for Wales, agrees Halfpenny's head was in the wrong position for the tackle.
"His tackling technique is poor," Davies told BBC Wales Sport's Scrum V programme.
"He's brave as they come. He never shirks a tackle, but I'm slightly worried now at the amount of times I see him hit his head on the wrong side.
"If you get proper tackle technique you put your head in the right place.
"A lot of players have had bangs on the head and then they've been told to retire and that would be a shame."
Scrum V's Ross Harries told television viewers during Saturday's match that Halfpenny "didn't need a head injury assessment because it was obvious from the knock he took on the pitch he was concussed".
Wales later confirmed Halfpenny was being treated for concussion.