NSWRL have been issued a formal warning by the NRL after an investigation into an HIA on Boyd Cordner found the Blues captain should not have cleared concussion protocols.

In a statement released on Friday afternoon the NRL said the 28-year-old Cordner should not have been allowed to return to the field in the State of Origin opener after copping another troubling head knock.

Seen stumbling to his feet in the 18th minute before he was guided to the sideline, Cordner then passed the SCAT assessment administered by the NSWRL medic, Dr Nathan Gibbs, in the dressing room at Adelaide Oval.

He returned to the field to play an additional 48 minutes in the 18-14 loss to Queensland.

However, the NRL determined that since Cordner showed signs of motor incoordination it was a ‘category one injury’ and he should have been immediately ruled out, regardless of the results of the SCAT assessment.

The NRL said it had considered the subjective nature of classifying symptoms and acknowledged the professionalism of all medical staff involved.

“In our view Boyd should not have been allowed to return to the field,” NRL chief executive Andrew Abdo said.

“Our chief medical officer spoke directly with both NSW and Queensland medical staff prior to Wednesday night’s game and reminded them of our high expectations in this area.”

The Blues have previously insisted Dr Gibbs followed NRL concussion protocols and Cordner passed all tests to return to the field. They have strongly denied putting the player at risk.

The NRL’s verdict comes after Cordner ruled himself out of the final two games of the Origin series to focus on his health and recovery following the head knock.

There are growing concerns for the Sydney Roosters captain who has suffered multiple concussions and spent seven games sidelined this season as a precaution.

One of those was a five-week break following a head knock at training, from which he had ongoing concussion symptoms.