Collingwood coach Mick Malthouse has welcomed the new interchange rules, but accused the AFL of inconsistency over the decision to introduce them mid-season.

Under changes announced this week, which will be used for the first time when the Magpies take on Geelong at the MCG next Friday night, a team will be awarded a free kick and 50m penalty if an extra opposition player enters the field.

Malthouse said the change was a good idea after the existing rules, in which the opposition captain has to call for a head count, were exposed as outdated when Sydney went unpenalised for fielding an extra man late in their round-seven draw with North Melbourne.

But he was irked that the league had changed its tune about altering rules mid-season, after telling him in past instances they would not do so.

"Two years ago I'm sure I rang someone from the AFL, I'm not going to say who, and suggested that we have got to seriously look at whatever (rule) I was talking about," Malthouse said.

"The word was we do not change rules or procedures during the football season.

"... I'm not complaining about it, I just think you can't tell me with one breath that you don't change the rules and a year later you do."

It is not the first time this year the Magpies coach has criticised the league in relation to interchange rules, having described a pre-season cap on player substitutions as a "stupid rule" created by "stupid people", a comment he later apologised for.

Malthouse said with a bit of forethought, the new system could have been brought in between seasons.

"It's a pity though that on last year's evidence that it wasn't done by round one," he said.

But he said the change was needed, given clubs had been taking advantage of loose policing of the interchange area.

"All things that you can start taking advantage of, clubs, coaches, players take advantage of it," he said.

Adelaide coach Neil Craig said clubs would be using this weekend's round as a rehearsal ahead of the new penalties being introduced.

Both he and Malthouse said their football departments would be putting plenty of effort into ensuring they got it right, given the penalty amounted to an automatic shot at goal.

"We've got a week to get good at it and make sure our procedures are really crystal clear from people on the bench to our support staff," Craig said.

"I don't think it's confusing, it's pretty clear, it just means that before a player goes on he's got to be given permission to go on because of what happened a few weeks ago.

"The clubs, coaches and teams created that issue so now we've been pulled into line."

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