Richmond coach Terry Wallace is formulating a plan for the AFL to return to the ancient 19th and 20th men, with a modern twist.

The Richmond coach is preparing a paper for the AFL that addresses the boom trend of interchange rotations, which aim to keep players fresh during a match.

Several coaches were unhappy during the pre-season when the league, worried about the pace of the game, experimented with restricting the number of interchanges per match.

Wallace is worried that even with four men on the bench, there are often so many rotations in a game that a team cannot keep pace with the opposition if it loses a man through injury.

As he puts it, one injury means a team effectively loses 25 per cent of its rotation ability.

It might still have 18 men on the ground, but it is almost playing one short.

Before unrestricted interchange, the AFL only had the 19th and 20th man on the bench and if they were used, the player who came off could not return to the game.

Wallace wants to retain the current system of four men on the bench during a game and also introduce two emergencies - or the 23rd and 24th men.

If they were used, the players whom they replaced would be on the bench for the remainder of the game.

"If you just had two emergency players, it adds another little bit of intrigue to the game, you can use them in any capacity that you want - if you want to use them early, later, it's up to you how you use them," he said.

"It doesn't necessarily need to be from an injury point of view."

Collingwood coach Mick Malthouse, a strong advocate of rotations, praised Wallace for his idea.

"It's got great merit - Terry Wallace is a great thinker in the game, he comes up with some very, very relevant and thoughtful ideas," he said.

"I'd like to think most coaches put the hat on for the competition, as opposed to their own club, and Terry is one of those blokes."

Like Wallace, Malthouse wants the random nature of injuries during a match to have as little impact on the result as possible.

"It would be a shame to see sides trying to struggle through under the present circumstances of interchanges, but lose players and then are totally disadvantaged and they lose the game ... because they just can't go with the opposition," he said.

"I don't know of any team sport - I'm going to be wrong here, for sure - that has a (low) ratio that we've got of players on the bench compared to playing."

Wallace said the game's tactics were in a state of flux, something he is noticing even since this season started.

"It's changed, it's changed very quickly - I've noticed from a coaching point of view, the game has changed in the last fortnight, it's changing that quick," he said.

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