The NRL will experiment with using differential penalties for incorrect play-the-balls in the upcoming trials matches ahead of the new season.

NRL head of football Todd Greenberg said the ruck area needed urgent regulation and that the success of the rule change in the trials would determine whether it stays on for the new season.

"It is a relatively minor offence but it is a source of frustration for many and it is clear there needs to be some penalty applied for failing to make a genuine attempt to play the ball," Greenberg said.

"We understand how critical penalties can be in the context of a game, but a differential penalty will ensure that referees can apply the rules more vigilantly."

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The NRL has also moved to deny teams forming walls to prevent charge-downs on field goals attempts, with referees now able to penalise offending defences for obstruction, beginning immediately.

"If two or more players form a wall (side by side) next to the play the ball and don't allow the opportunity for a defending player to move directly towards the player in possession, the referee will penalise for obstruction," the new rule states.

The anticipated shot clock will also be in use during this Saturday's All Star clash in Brisbane, as well as the Charity Shield match between St George-Illawarra and South Sydney.

Teams now have 35 seconds for scrums and 30 seconds for dropouts, or else the offending team will give away a penalty.

- AAP