Captain's challenge gets early approval but work to do

St George Illawarra are set to explore their options in a bid to be successful in the new captain's challenge rule in 2020 after a strong start in the Charity Shield clash on Saturday.

Dragons coach Paul McGregor confirmed the coaching staff were working on a system with the players to help have more say on whether to challenge an on-field decision live in play.

The Dragons successfully challenged two knock-on calls against the Rabbitohs to receive possession they otherwise wouldn't have been given in the 26-12 loss.

Under the new rule, teams have 10 seconds via their on-field captain to call for a review on plays like an error, one-on-one strip, offsides or obstruction.

It was suggested a green and red paddle may be used on the sideline in a bid to send an instant message from the sideline.

"We didn't have it tonight but we're looking at different ways to be innovative and bringing quick decisions where if we can get it from the top [of the coaches box] to the sideline," McGregor said.

"Or if the players see something and look to us to back up that support. We'll come up with different ways to make it clearer out there for sure."

Like most coaches, McGregor was eager to leave judgement on the new system until he saw it happen in real time.

"I did [like] it tonight, it worked well. There were a couple of others we probably could've challenged as well," he said.

"I think for something so fresh and new to get something right it's good. The boys are looking for it on the footy field and if they feel they can challenge something that will get the result they did.

"That's two possessions we wouldn't of had if we didn't have the captains challenge."

Meanwhile, Rabbitohs captain Adam Reynolds told NRL.com he would learn from his unsuccessful challenge and admitted he and Wayne Bennett were left confused by the rule.

The Bunnies challenged a Trent Merrin knock-on call in the 36th minute that went against them.

"It was a bit of a blunder, we actually thought we had one per half," Reynolds said.

"Wayne said to use it before half-time and there was only a few minutes until the break so we'll learn from that.

"It's funny to look back on now, someone is calling me Tim Paine with the unsuccessful challenge."

The challenge came less than a minute after Ben Hunt called for a review but Reynolds said it didn't affect the flow of the game.

"I didn't think it took too long out on the field, I'm not sure how the viewers saw it sitting at home though," Reynolds said.

"The Dragons used it to full effect and got a couple of turnovers. In hindsight, the decisions were either overruled or considered correct so it can only be good for the game."