St George Illawarra have defended themselves against accusations they flouted concussion rules and allowed Josh Dugan to stay on when he should have been taken off the field.

Play was stopped for at least a minute when Dugan was laid out on the Southern Cross Group Stadium turf during his side's gutsy 16-10 win over local rivals Cronulla on Sunday night.

The Dragons No.1 was allowed to play the next 71 minutes despite laying motionless after copping a stray elbow from teammate Russell Packer.

Sharks coach Shane Flanagan questioned why Dugan wasn't immediately pulled from the field to be tested for concussion, but Dragons counterpart Paul McGregor said the incident had nothing to do with concussion.

"I think it was a jaw injury not a head injury, that's the report I got back in the box," McGregor said.

"I've got Kurt Mann there (on the bench) so I've got a guy to put on straight away so it's not a big deal.

"He said it was his jaw so I back the medical staff there." Flanagan said while he had no proof Dugan suffered a concussion, he should have been pulled off to be assessed under the NRL's head knock protocols.

Josh Dugan Mark Kolbe/Getty Images

The Sharks were forced to play without second-rower Wade Graham for the final 20 minutes after he suffered a worrying head knock.

He came off in the first half after suffering a bump in a tackle and then had the football kicked into his head.

Graham returned after passing his head injury assessment but was later pulled by the trainer after appearing unwell and is no certainty to take on Parramatta on Saturday.

"Duges might not have had any signs of concussion but he did lay there prone, he might have been stunned," Flanagan said.

"We don't know that (if he had a concussion) but the rules state that if he lays prone he has to come off for a test."

It comes at a time when James McManus is suing former club Newcastle in the Supreme Court for the negligent management of head knocks during his career.

The Knights are expected to also come under scrutiny after they allowed fullback Brendan Elliot to play the rest of the game despite suffering a head knock in their loss to South Sydney.

Newcastle coach Nathan Brown renewed his case for an 18th man after his bench was reduced to two in their 24-18 loss to the Rabbitohs - a call backed up by Wests Tigers coach Jason Taylor.

While the NRL has stated they have no plans to introduce a concussion reserve, Taylor said the current rules could lead to more injuries.

Sauaso Sue and Chris Lawrence were forced from the field in the Tigers' 46-6 defeat to Canberra on Sunday.

Taylor said leaving tired players on the field could lead to further injuries.

"You've got players out there that are in a fatigued state and I suppose that they're more at risk of getting injured when they're playing like that," he said.