Trbojevic is expected to be one of the biggest exponents of the new ruck rule when the NRL returns this week.

The livewire fullback will likely be one of several No.1s to spend more time sniffing around the ruck, with quicker play expected through the middle when six-again is called.

The Sea Eagles led the NRL for tries created in the middle channel last year, largely off Addin Fonua-Blake and Martin Taupau's power and the speed of Trbojevic.

The 23-year-old knows that will become even more important in 2020, after averaging more than one line break per game for the past five years with most through the middle.

"On those six-again calls you're going to see a few more opportunities through the middle of the field," Trbojevic said.

"And as a fullback you want to do your best to exploit them."

Manly ranked fifth last year for scoring tries in sets coming from 20-metre taps, benefiting greatly from up-tempo play.

Most sides have found it difficult to train for the new rule, which will see the referee call an immediate six-again rather than stop play and blow a penalty.

Only the Sydney Roosters have a former NRL referee in Chris James in their bubble, with most sides sending video off to the NRL for analysis.

"Those quick play-the-balls and the feel of the six-again, you can't really train for them," Trbojevic said.

"It's hard to create them. It's more a thing you've got to experience on the field."

The rule comes after the NRL introduced a 20-40 and captain's challenge at the start of the season.

Meanwhile, Manly captain Daly Cherry-Evans believed the six-again policy could have more of an impact later on in games.

"If teams are getting half-a-dozen of those in a half, it's going to be really interesting to see what impact it has on a team in the second half," he said.

"Is (there) going to be a direct impact and people are scoring off the six-again, or maybe it's the fatigue factor that comes into the game later?"

HOW THE NRL LOOKS DIFFERENT FROM 2019

* One referee

* Six-again for ruck infringements

* 20-40s in play for kicking teams

* Captain's challenge

* Attacking players cannot be tackled in mid-air

Australian Associated Press