The NRL is set to crack down on dodgy play-the-balls in 2018, with chief executive Todd Greenberg responding to fan complaints.

The game's governing body sent a directive to all 16 clubs before Christmas telling them referees would scrutinise the ruck more heavily this year.

It's long been a bugbear of fans and commentators that players have been able to get away with not playing the ball with their foot or while not standing straight.

Greenberg said that would be tightly policed under new referees boss Bernard Sutton.

The clubs will have no cause for complaint because referees spent time with each club in the pre-season, letting them know what to expect.

"You will definitely see the rules tighten on the play-the-ball," Greenberg said.

"There was an edict given to clubs in the pre-season and I know the the referees have been at scrimmages with all of the clubs.

"There will be a much greater focus on the play-the-ball and playing it with a genuine attempt to play the ball.

"I think you'll see referees being quite vigilant on that. The challenge for the referees is to maintain that throughout the year."

Greenberg said he was reacting to fans' complaints about the policing of the play-the-ball, which had eroded during the past several years.

"There's little things and big things. Little things like the play-the-ball is the big things to fans," Greenberg said.

"The feedback I had last year when I went to fan forums was not to do with the finances. It was to do with the play-the-ball and referees and judiciary.

"We listen carefully and we've spoken about it with the competition committee, we've spoken about it the coaches and the referees have been given strong directives."