Marshall was captain of the NRL All Stars side in 2012 against the Indigenous All Stars, which featured an experiment with the radical rule for the only time.

League central had floated the possibility of introducing the rule into the competition but hadn't gained the support of coaches.

Eight years on and the league community waits with baited breath on what kind of impact the innovation will have when the season returns this week.

Rival coaches have been scrambling to get their hands on tape of the annual pre-season fixture to try to make the necessary adjustments to their systems.

"I was tired. It was in the pre-season and I wasn't up to physical shape to play again. It was a bit tough," Marshall said on Monday as he recalled the match.

"It could help the game get a bit quicker.

"But I suppose for all of us, there's a lot of unknown."

Under the new rules, referees will restart the tackle count for ruck infringements instead of temporarily halting play to blow a penalty.

That could leave defensive units vulnerable if forced to defend multiple sets.

"Defending a set of six on its own is pretty tough but then, when you throw into the mix a six-again, it definitely takes a lot of your juice out," Marshall said.

"There'll be times you're defending two-three sets in a row without the ball. That's going to catch up with you at some stage.

"So I guess you're going to see more teams fighting harder in the play-the-balls and try and exploit that rule by getting more six-again (calls).

"It could open up and seriously make it a better spectacle than it already was."

Australian Associated Press