Penrith coach Ivan Cleary is a fan of taking the heat off NRL referees with the captain's challenge but he's unsure if it's going to be a success when its rolled out this season.
Cleary sits on the league's competition committee, which vetoed the proposal late last year before the ARL Commission opted to push through with the rule change.
At the time, there were no guidelines as to how the idea would be implemented.
"No one really knew how it was going to work," Cleary told AAP.
"(So) it's on the commission, which is fine.
"As a coach, I would say there is a lot of uncertainty around it. We haven't even broached it with (our) players yet.
"I hope it's not too bad (but) I think there's going to be a lot of confusion."
The league got its first taste of the challenge system at a top level during Saturday's annual All Stars match on the Gold Coast with mixed success.
Maori captain Adam Blair was unsuccessful with his challenge, while Indigenous skipper Joel Thompson got knocked back because it wasn't during a stop in play.
The NRL will get one final look at the hastily introduced rule change during Saturday's Charity Shield match before it is officially approved next week.
It would be one of the rare occasions the ARLC tinkers with the laws of the game without the approval of the competition committee.
In theory, Cleary is supportive of the idea and he likes the NFL model, where video replays aren't used until a challenge by a team.
However, he also sees the need to eradicate the howler in try-scoring situations.
"I was actually a fan of doing it like the NFL, where we don't have the video unless your captain's challenging something," Cleary said.
"It's a bit like cricket; you might get two or whatever it is. You keep going until you get one wrong.
"I wouldn't mind that (because) I'm a bit old-fashioned.
"I get it if it's a try-scoring situation, you'd probably want to get that right.
"I don't mind the concept of taking a bit of heat off the refs and putting it on the players.
"I'm just not sure whether this way is the best way.
Australian Associated Press