Parramatta coach Jason Ryles warned in Round 3 that changes to NRL rules could contribute to player fatigue and more hip-drop tackles.
He made the comments after J'maine Hopgood suffered a season-ending ACL injury in a hip-drop tackle, arguing that more set-restarts instead of penalties could leave players tired.
Billy Slater has now raised concerns about the rules after Phoenix Crossland's tackle broke Nathan Cleary's leg.
Speaking on the Billy Slater podcast on Monday, Slater said Crossland was responsible for the tackle but that the NRL also had some responsibility.
"I do feel that the game (the NRL) has a little bit of responsibility in this as well," he said.
"When you change interpretations and rules you always have a flow-on effect."
Slater argued that protections for playmakers and kickers can make defenders hesitate, leaving them to tackle at the last moment.
"If you think about the protection of ball players and kickers and not being able to tackle them even fractionally after they pass the ball now. Ten or 15 years ago that tackle would not have happened because Crossland would have had more speed and force going into that tackle."
He said Crossland would usually have run in from inside and tackled Cleary front-on, but feared hitting him after he passed the ball.
"But because he was worried about tackling Nathan after he'd passed the ball he was actually in a passive position and passive mindset. All of a sudden Nathan threw a dummy and he had to make a tackle and he didn't have that force behind him."
Slater said the hesitation left Crossland without the momentum to respond when Cleary dummied and ran.
"I have no doubt that contributed to why Phoenix Crossland is in this 'grabbing and sitting down' position because he doesn't have that momentum and force and mindset of making a tackle."
Newcastle entered a guilty plea before Crossland's judiciary hearing on Tuesday night, ruling him out of the NRL grand final against the Roosters.
He is likely to receive at least a four-game ban, which would cost him most of the World Cup with New Zealand.