Demetriou's comments came after the NRL made the biggest change to its concussion policy in almost a decade, announcing on Wednesday any player who suffers a head knock will be subject to an 11-day lay-off.
The rule will be implemented in conjunction with current head injury assessment protocols where an independent doctor is employed at each game and conducts mid-game testing for players deemed to be experiencing symptoms.Â
The new rule comes after Newcastle five-eighth Kalyn Ponga suffered a fourth concussion in 10 months during round two, sparking ongoing speculation about his immediate future in the game.
Demetriou applauded the NRL for safeguarding its players and sticking to the science.
He believes the NRL is adapting its concussion rules as soundly as possible, given the inherent physicality of a game that is only getting faster and more brutal.
The coach says modern players must realise they are in safe hands.
"There's a lot of hysteria around concussion at the moment and a lot of it's fear-mongering to be honest," he said.
"Players that play the game need to understand that it is a contact sport.
"There's risk in contact sport and these players are looked after better now than they've ever been and rightfully so.
"These problems that players have had from the old days, these guys that are playing now, they won't have these problems because the game as it should be is looking after them."
Demetriou encouraged his players to shut the outside noise out as concussion again proves a hot-button issue only three rounds into the season.
"A lot of ex-players are getting involved and having an opinion on a lot of things that they don't have the medical training to have advice on," he said.
"I think what we have to do, and I say this to the press as well, we've got to let the doctors make the decisions.
"The NRL has taken the advice from them and so they should. It's good to see."
The Sydney Roosters have led the NRL in managing players with concussion history as extensive as in the case of Ponga, who would likely need more than 11 days to recover if struck down again.
In 2021, the club supported senior players Boyd Cordner and Jake Friend in their decision to retire following repeated head knocks, and gave Luke Keary six weeks off last season to recover from his latest concussion.
Coach Trent Robinson said the NRL's latest concussion rule struck the right balance between monitoring player welfare and empowering clubs to manage their own players who had longer concussion history.
"It's hard to mandate those ones," Robinson said.
"You can't ask the NRL to do that, that's up to the club doctors and the club to do their work, and independent specialists that we use as well to say what's best when there's been multiple or lingering symptoms.
"It's a pretty serious injury to the brain but it's like any other injury, you can't mandate on hamstrings or shoulders or anything like that.
"There's a lot of care in clubs. You've got to leave it up to them to take care of that."
