Parramatta co-captain Tim Mannah admits he is concerned the NRL's new concussion laws could be exploited by teams wanting a free interchange.

Mannah is pleased the game is prioritising player welfare but says the new rules should be treated more as a trial than the final solution.

The front rower was stunned for a moment and unable to get to his feet early in Sunday's clash with the Warriors, and was taken from the field for cognitive testing under the strict new guidelines.

After sitting the concussion test which takes 8 to 10 minutes, the club doctor cleared Mannah to return to the field inside the 15-minute allocated period, meaning his time off the field, with Darcy Lussick on in his place, did not count for an interchange.

Mannah was one of only two players from round one matches who was passed to return, while the other six were ruled out and their interchanges counted when they could not come back within 15 minutes.

Although Parramatta could in no way be accused of manipulating the system, Mannah warned it could be something the NRL needs to look out for.

"Because you get free interchanges, I think down the track they've got to make sure with how they determine how bad the concussion is," Mannah said.

"If you get dazy do you get off? Concussed? You just have to look at the degrees of concussion.

"I think it's great they're considering the player welfare, it's awesome.

"What the best way of doing it is, I'm not sure. It's a bit of a trial to see how this goes because I think there's potential for it to not work out as good as they hoped, so you just have to wait and see I guess."

Graham confused by Mead ruling

Mannah is not the only NRL player with some queries to come out of the opening week of action.

Cronulla star Wade Graham said after Monday night's clash with Gold Coast that he was puzzled as to why opposition winger David Mead was not taken off for assessment despite staying down long enough after a high shot for a penalty to be awarded.

"The bloke stayed down, they've had a check upstairs and they've found there was contact with the head," said five-eighth Graham.

"I don't know what the new five-point-plan is but obviously, staying down, there's got to be an indication he's hurt and if there's head contact, it's got to be something with the head.

"I was a bit confused by that."

AAP