There were worrying scenes in the opening minutes of Wales' Six Nations clash with France as Tomos Williams appeared to suffer a serious head injury.
The scrum-half struggled to get to his feet after tackling Jonathan Danty, and was clearly concussed after getting his head on the wrong side of the French centre.
Williams tried to stand after the incident before collapsing to the turf again.
He then staggered back into the Welsh defensive line, looking alarmingly dazed. He was permanently replaced moments later by Kieran Hardy.
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The game was not stopped as Williams lay face down on the Principality turf, with France scoring the first try of the game moments later through Anthony Jelonch.
TV viewers expressed their horror at the incident on social media, with many asking why the game was not stopped immediately.
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Loosehead Gareth Thomas also left the pitch for an HIA ten minutes later, after being hit in the head by the knee of Antoine Dupont as he tried to bring down the French scrum-half.
The incident comes just a fortnight after similar scenes at Twickenham, when Welsh front row Tomas Francis was seen staggering and holding himself up on his own posts following a clash of heads with teammate Owen Watkin.
Francis initially remained on the pitch after being checked by a medic before being removed to undergo a HIA, which he duly passed before returning to the pitch around 10 minutes later, and played on until he was replaced by Leon Brown in the 56th minute.
But, under World Rugby laws, any player who shows visible signs of balance disturbance/ataxia after a head blow should be removed immediately and permanently from a match without a HIA.
In an open letter to the Welsh Rugby Union, World Rugby and Six Nations bosses, lobby group Progressive Rugby, which is made up of a number of former and current players, as well as medical experts, described what unfolded as "a clear and flagrant breach of HIA protocol"
This was followed up with more criticism from Professor John Fairclough, a leading surgeon who previously worked with the WRU, who said it would be a "grave mistake" were Francis to be selected for the clash with France.
However, ahead of Friday's game, Wayne Pivac defended his selection of Francis, offering some clarity over the situation at his pre-match press conference.
"So just wanted to make a couple of points on Tomas Francis," he said. "Firstly, I just want to point out that we’ve got a very experienced medical team who we think are world-class. They’re experts in their field.
"In relation to Tomas Francis and also Josh Adams actually, both of those players have been seen by our medical team after the game, the follow-up protocols and the return-to-play guidelines set by World Rugby have been followed closely.
"At each stage of those processes, they’ve come through fine. As a result, we’ve gone the extra mile with Tomas and got an independent concussion specialist involved.
"He’s got the history of the player and also had a look at the footage from the match. He’s been taken though the protocols which we’ve followed, which are World Rugby’s protocols.
"He’s supportive that the player is clear to be selected. On that basis, and in consultation with the player, we’ve decided to select Tomas Francis."
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