World Rugby will seek answers from the Rugby Football Union (RFU) after expressing its disappointment that Northampton Saints allowed George North to return to the field after seemingly being knocked out during a Premiership match.
North has a history of suffering head injuries, but the Wales wing was given the green light to go back on despite appearing to lose consciousness during a clash with Leicester Tigers this month.
The flyer underwent a Head Injury Assessment and Saints' medical team later accepted that he ought not to have been allowed to return to the fray.
A Concussion Management Review Group (CMRG), set up by Premiership Rugby and the Rugby Football Union, ruled that North should not have played on, but opted against taking any action against the club or individuals.
Governing body World Rugby waded in with their response to the handling of the incident by releasing a stern statement on Friday.
The statement said: "World Rugby's number one priority is player welfare and our primary concern is the welfare of George and all players.
"It is therefore disappointing that apparent non-compliance with the sport's elite head injury protocols led to George remaining on the field of play when he should have been immediately and permanently removed.
"World Rugby's recognise and remove protocols state in no uncertain terms that any player displaying clear or suspected signs of loss of consciousness should be permanently and immediately removed from the field of play. In this case, the Head Injury Assessment should not have been undertaken.
"Unions and tournament organisers can access the Head Injury Assessment process for elite competitions, subject to World Rugby's player welfare tournament standards criteria being met.
"In this incident, it is clear that there was a failure to comply with these robust and well-established protocols, which continue to successfully protect players around the world.
"Specifically, failure in the identification and management of the injury and due consideration of risk when considering North's history were at fault in this unfortunate case."
The statement continued: "While recognising that there is always a risk of human error, we will seek further information from the RFU regarding the factors behind the apparent non-compliance with World Rugby protocols and the outcomes reached by the independent review group.
"World Rugby will also continue to work proactively with its unions to ensure best-practice is implemented and followed in order to reduce the risk of a repeat incident within elite competitions."