England coach Eddie Jones has called on rugby union's lawmakers to implement measures to speed up the game and increase fatigue, including reducing the number of permitted replacements in matches from eight to six.
Jones said lengthy television reviews and debates with referees have provided players with extended breaks and prevented them from tiring out, reducing spaces for teams to attack in late-game situations.
"We have let fatigue go out of the game," Jones told British media. "Apart from increasing the reserves to eight, we have had to have head-injury assessment, which has slowed the game down.
"We have had increased television match official (TMO) involvement and more protocols and we have encouraged referees to be debaters."
Jones said that the sport is slowly beginning to resemble American football with its frequent stoppages.
"We have got to get fatigue back, because we need space. Otherwise we will end up like the NFL. I support going down to six replacements and encouraging referees to make a decision and get on with the game," he added.
"We have to find some way to tidy up the TMO. You only have to watch rugby league in Australia where it is clear and concise: one or two looks and a referee knows if a try can be awarded."