Cardiff - Wales wing George North should not have continued playing after his head injury in Friday's Six Nations opener against England, World Rugby has said on Tuesday.
But the sport's governing body exonerated the Welsh Rugby Union (WRU) of any blame in their handling of the player.
North took an accidental boot to the head from England lock Dave Attwood in the first half in Cardiff and he was temporarily replaced by Liam Williams while he underwent a mandatory concussion assessment.
The 22-year-old subsequently returned to the field, but he then clashed heads with team-mate Richard Hibbard during the second half in what appeared to be a more serious incident.
North did not go off a second time, playing on as England started their Six Nations season with a 21-16 victory.
According to World Rugby, North "should not have remained on the field of play" as the "World Rugby head injury protocol clearly states that a player should be immediately and permanently removed from the field of play where there are any visible symptoms or suspicion of a potential concussion".
But World Rugby said the WRU had followed correct protocol, accepting its explanation that "neither the team medical staff nor the independent doctor had sight of the incident" and that they "would have taken a different course of action had they had direct pitch-side visibility or access to the same broadcast footage seen by those watching on television".
World Rugby also said that it will be "immediately investigating, evaluating and promoting the implementation" of new measures.
Wales resume their Six Nations campaign against Scotland at Murrayfield on Sunday and North still hopes to be passed fit to feature.
"George is completely symptom-free. He is going through the return-to-play protocol," Wales assistant coach Robin McBryde told a press conference at the Wales squad's training base in Hensol near Cardiff.
Meanwhile, Wales centre and qualified doctor Jamie Roberts has voiced optimism that the debate sparked by North's injury will help make the sport safer.
"A lot has been made of it, and rightly so," Roberts said.
"Concussion is a huge part of the game at the moment, and hopefully moving forward, the protocols that we put in place -- from our side, there will be video replays now for the medical staff at home and away matches -- are going to make the game safer for the players involved."