While there has been plenty of opposition to the trial interchange cap during the NAB Cup, the League chief said on Tuesday morning the AFL Commission had already decided to introduce the rule permanently in 2014.
However, Demetriou said the Commission would assess the data and the results from the injury survey before deciding on the appropriate figure.
"Unless people have got amnesia, the AFL Commission has already passed the rule that said the cap's coming in," Demetriou said on SEN.
"There will be a cap. That's already been decided. People can ark up and argue with each other and so forth but I'm not quite sure (what the problem is)."
There has been a steady flow of opposition to the rule, headed by Carlton coach Mick Malthouse who slammed the AFL's Laws of the Game Committee for being out of touch with the modern game.
"I sincerely hope that the rules committee are governed by people, who have got an understanding of the modern game, not previous long-ago coaches, or long-ago players, or new players that have no say, or new officials that just make up the numbers," Malthouse said.
Malthouse is strictly opposed to the restriction of 80 interchanges and has accepted an invitation from committee member Kevin Bartlett to meet on Wednesday to discuss his concerns.
Hawks counterpart Alastair Clarkson urged the League to be cautious when introducing the cap.
"It's a pretty dramatic change to go to 80," Clarkson said.
"No-one really knows what's going to happen to the game.
"Hopefully common sense will prevail and if they want to introduce a cap, then they cap it at something sensible like 120."
However, Brisbane Lions coach Michael Voss said the reduced rotations assisted in preparing players for increased intensity of the home and away season.
"The one advantage you get with 80 rotations is that … players are spending more time on the field," he said.
"For mine, having players out there playing for long minutes prepares them all a little bit better I think, in terms of round one and being able to handle that intensity and game time they need."
There were, on average, 131 interchange rotations per game during the 2012 season.
The trial figure of 80 chosen by the AFL is based on the 2008 average.
As revealed on AFL.com.au on Sunday, the Sydney Swans actually breached the interchange cap - on purpose - in the final minutes of their game against St Kilda at Etihad Stadium.
While it was highlighted on the television coverage - the Swans made 23 interchanges in the final quarter, instead of the allowed 20 - it was later confirmed the Swans and the AFL match day manager were aware of the infringement.
Under the interchange rule, a club is permitted, in theory, to make a maximum of 23 interchanges for the quarter - under the provision that those players coming off the ground must sit off for a period of 15 minutes.
