Reverting to one referee and introducing a six-again option for ruck infringements were the contentious on-field topics ahead of the NRL's return on Thursday.

But the fine-tuning has so far been warmly received by players, coaches and fans who have sung the praises of a more free-flowing game.

Respected former whistleblowers Mander and Harrigan have long called for the return to a single referee but accept the widespread praise for officials will only last so long.

"Public opinion about referees will chop and change, it doesn't matter what they do they'll be criticised," Mander, now deputy leader of the opposition in Queensland, told AAP.

"But there was no reason to have two referees; it didn't add any value and it could be argued that it complicated things."

Mander believes that constant tweaks and additions to the refereeing structure during his 13 years in the game never helped in the NRL's "quest for perfection".

"The six-again takes an opportunity away from the cameras and commentators to analyse the decision and that's a good thing; it allows the ref to have some discretion," he said.

"But we're going to have to wait a few more games, maybe the whole season, to see how it goes because it's when it comes to the pressure at the end of a game and score is 20-18.

"It's not until we see that penalty that it becomes contentious."

Whether referees award six-again or blow a penalty looms as a boiling point but Mander insists that's where the one-referee system can help.

"Refereeing is instinctual ... that's the art of refereeing," he said.

"It's not just in or out; you have to have a vibe for the game and feel that they don't want a penalty now or that they do.

Bill Harrigan agreed, saying a solo referee's "empathy for the game" would enhance the product.

While thrilled with the recent rule changes he was careful to reserve his judgement as teams begin to pick them apart.

"The punters that I'm talking to are all saying 'cool, it's great, loving it'," he told AAP.

"But it's only one round; you're going to get coaches studying it and saying 'OK, how can we get around it and put our little tweak on it?'."

Australian Associated Press