Edwards was concussed for the second straight game when he was stretchered from the field in the sixth minute of Saturday night's 12-6 away loss to the Penrith Panthers.

The 25-year-old will have a head scan to check for possible bleeding on the brain and is unlikely to face his former side, the Newcastle Knights, at Canberra Stadium on Saturday.

Although the NRL doesn't have any rule stopping players taking the field the following week after a concussion, Lo said it would be common sense for Edwards to be rested after a ''severe concussion''.

Lo examined Edwards on Sunday morning and said he was feeling normal, a vast improvement immediately after the hit when he lost consciousness and was confused when he woke up. He was consoled by his mother and brother in the team's dressing room.

Edwards had to pass a series of concussion tests to play after he was knocked out against South Sydney the previous week.

"It's hard because with all the medical evidence and all the concussion tests we have to do ... he passed them the week before and he seemed good,'' Lo said.

''The question is, if someone has another concussion is it because he wasn't 100 per cent from the previous week or would have anyone had such a nasty concussion from such a big hit?

''With the current testing that we have, it's probably not good enough, but that's all we have to work on.''

Edwards underwent a "sports concussion assessment tool (3) test" once he was taken off the ground against South Sydney.

Under NRL rules brought in this year, doctors have 15 minutes to administer the test before deciding whether the player can return to the field.

The AFL has a 20-minute limit, while Super Rugby has a condensed version of the test, minus questions about a player's memory, which only takes five minutes.

During the week, he completed a "digit symbol subsitution test" before he was allowed to resume training.

Edwards underwent cognititve testing on a computer a couple of days later before he took part in contact drills and was eventually cleared to play against the Panthers.

Lo said the NRL was moving in the right direction by bringing in the concussion tests and that club doctors had been invited to provide feedback so they could be improved.

One of his ideas was to bring in rugby-league specific drills, such as throwing and catching a ball and smashing into tackle bags, as part of the SCAT 3 test.

''The problem is, you can do all these things on paper, but when some people start to exercise, the symptons come back, they get worse,'' Lo said.

"I'm really glad they [the NRL] have brought them in, they've been really good with this.

"They said the first year there will be some issues and things that can be improved, and we want you guys to have a look at it.''