The AFL's concussion crackdown could prompt clubs to deliberately misdiagnose players or force others out of action unnecessarily, the league has been warned.

Mirroring widespread discontent with the planned new interchange rules, Tuesday's AFL announcement that concussed players will be banned from returning to the field was mostly poorly received.

Carlton captain Chris Judd said the stricter policy - released two days before the season-opener - might cause clubs to avoid diagnosing the condition, rather than lose a player.

"You'll just never get anyone concussed anymore," Judd said.

The reigning Brownlow Medallist said the crackdown could compound the difficulty clubs faced managing the reduction from four interchange players, to three plus a substitute.

"The risk is that if clubs use that sub too early and then get some injuries they may be tempted or forced to put injured players back out on the field," he said.

"I think that would be a concern of everybody's if the player's got concussion or something like that."

Essendon club doctor Bruce Reid also predicted the combination of the new concussion rule and interchange system could create problems.

Reid said it could take up to 15 minutes to accurately diagnose concussion.

A team could not afford to be down a player on interchange for that long, forcing them to use their substitute.

But that would mean having the replaced player banned from returning, when they might eventually be found not to be concussed.

"You're just going to have to rule out everyone who has a dizzy spell," Reid told SEN radio.

But Geelong doctor Chris Bradshaw said having a clear-cut rule would help, as it would take the pressure off medical staff to make a call on whether a player could return.

The most notable case of a concussed player returning to the field last season was a horrific incident in which Hawthorn's Jordan Lewis copped a huge head knock from flying Western Bulldog Jarrod Harbrow.

While Lewis was clearly hampered, Hawks captain Luke Hodge said there was enough evidence pointing the other way to mount a case against a black-and-white rule.

"Some concussions are really bad and you can't come back on the ground," he said.

"But we've seen in the past that if you sit down for a couple of quarters then you're okay, and if you do pass the test, then you're able to come back on."

Sydney veteran Ryan O'Keefe also said concussion was a "grey area" and the new rule could add another complication to the new interchange system.

"It's harder for the coaches really," he said.

"If a player has a concussion and they have a sub player, I think it's going to make coaching tactically a lot harder and tie their hands."

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