AFL interchange numbers are set to stay high as clubs try to find a way around the controversial new substitute system.

But league operations manager Adrian Anderson is less concerned about that statistic and more interested in how the new rule will affect the way the game is played.

This season, one of the four interchange players for each team will be a substitute only, meaning the player he replaces is out of the game.

Clubs have dramatically increased their bench rotations and the AFL is worried this has led to more congestion in play and a greater risk of injuries.

"I don't think there's any number and I suspect that interchange numbers themselves may stay high," Anderson said.

"But what's relevant from our point of view is that the rest they're getting - you can't physically get as much rest for the players and keep them going at the same pace."

The league will look at several factors as they assess the new rule, including player speed, on-field congestion, injury rates and whether substitutes affect the fairness of a game.

Anderson is also expecting plenty of criticism as clubs adapt to the new interchange rule.

"I'm confident as I can be that it's been made on the basis of solid research, data and the best available information at the time for the best and right intention," he said.

"You can never be 100 per cent certain.

"What I am 100 per cent certain about is there will be the usual cries that it's the end of the game and that sort of thing."

He would not comment on whether the league might look at capping interchange numbers next season, depending on how the substitute system works.

"I'm not going to rule anything in or out at this stagem," he said.

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