The revolution sweeping through rugby could include a reduction in the number of replacements allowed during a match.
As the southern hemisphere countries contemplate major changes to the competition structures, World Rugby is turning its sights to the replacement rule.
A number of leading figures in the game, including England coach Eddie Jones, are advocating for the change so as to introduce more fatigue into the game.
This in turn would open up attacking opportunities. A reduced number of replacements would mean fewer interruptions to matches, and there is also a belief in some quarters that the current rule leads to more injuries.
The Telegraph has reported World Rugby is sifting through data from major leagues including Super Rugby as it contemplates making the change.
At the moment, eight replacements are allowed for each side and Jones believes this should be cut by two.
"We have got to get some fatigue back into the game, we have got to get some space back into the game because otherwise we will end up with NFL," he said this week.
"I would put the game down to six replacements and the referees less communicating about decisions and get on with the game. And I think we have got to find out some way to tidy up the TMO (video ref)."
Former England hooker Brian Moore is among those saying a cut will improve safety. The current rule meant that too many big and fresh players were charging into the game against tired opponents.
Another former England player, Jeremy Guscott, and top referee Nigel Owens are also backing the change.
World Rugby's chief medical officer Dr Éanna Falvey said the world body was trying to use good data rather than emotion to base decisions on.
He said teams would still need three specialist frontrowers on the bench for scrum safety reasons.
"It limits your options, basically," he said.
"The real issue is whether or not you are prepared to cut down on replacements and having to play without specialist position players like a nine or a 10, because you might need to have a utility back.
"Our first step with this is to know whether reducing substitutions makes a big difference to the injury rate and pace of the game, and if it does, to start looking at the practical solutions to that problem."
He said a rule change could also lead to body shape changes.
"…bigger players may need to play for 80 minutes rather than 55, which means a player can't necessarily be 10kg heavier because he won't be able to get around for the final 20 minutes," he said.
"The downside is that it may promote more injuries in those players while they are adapting and getting up to speed. But the upside would be that you have lighter players who are more mobile, and able to get around more.
"The argument would be that if you have players who are not quite as explosive, you might see a cut down in the number of injuries.
"But, the reason we have substitutions in the first place is to prevent injuries. It's difficult to know where the trade-off is with this."