Yeo suffered his second blow to the head in as many weeks during Saturday's win over Newcastle. In coming days, he will see a specialist to be assessed.

It was originally thought he had been ruled out for the rest of the game after leaving the field in the third minute, having copped a stray elbow from teammate Sione Katoa.

The sight of the Panthers' back-rower running back on at the 29-minute mark raised eyebrows, given it came outside the required 15-minute period to undergo a head injury assessment (HIA) and apply for the free interchange.

The club insisted Yeo passed his HIA test but was delayed in returning to the fray because he was having stitches applied to a head wound.

"We have asked for a report from the doctor and head trainer regarding the process when Isaah was assessed after he came off and the decision-making process to allow him to return to the field," NRL head of football Graham Annesley said.

"We are not going to jump to any conclusions about that. We have to get the appropriate medical advice from the officials who assessed him. Our rules around the treatment of head injuries are very specific."

The incident came just a week after he was left concussed by a high shot from Parramatta's Michael Jennings.

Annesley said Yeo might be allowed to play Melbourne on Saturday in Bathurst if he passed testing during the week.

He said the NRL had not considering mandatory stand-downs, however Yeo would have to be passed fit before he could return to playing and training.

Concussion has again been a hot topic in the league over the opening fortnight after Immortal Andrew Johns' claim that his recent battle with epilepsy might have been a result of repeated head knocks over his career.

St George Illawarra veteran James Graham on Monday issued a strongly worded statement in reaction to a Sydney Morning Herald opinion piece which claimed he didn't take concussion seriously.

Graham drew criticism for suggesting players should play Oztag as an alternative to avoiding concussions but pointed out he had read and consulted heavily on the issue.

Australian Associated Press