WESTERN Bulldogs coach Luke Beveridge has slammed the AFL's new medical substitute, saying the "very rushed" rule will cause a series of "headaches" for clubs.

The rule was raised at last week's meeting between the coaches and League but with Beveridge absent from that discussion, he said it had been a shock to see the new rule introduced just a day before the start of the season.

Clubs will be able to replace a player deemed to have suffered an injury or concussion symptoms at any stage of the game with the substitute, but the 2016 premiership coach said it was a mistake. 

"It's been rushed through. As of yesterday, our medical staff hadn't been briefed and are none the wiser on the operational aspect of it," Beveridge said on Thursday ahead of his team's season-opener on Friday night against Collingwood. 

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"And so when you've got the whole medical establishment not being briefed and going into the competition, it's just been rushed through. If we've got to a stage where we're saying more players will come out of the game through an injury or concussion than ever before that we need to have an extra player on hand, then surely there are some other levers to pull than just introducing a substitute player.

"We've been down this track before with the old sub. The 75 interchanges as a constraint and I wouldn't think any of us as coaches would want to use more than four on the interchange bench because it means players are off the ground for too long. 

"So maybe they could have just added a fifth where both teams have got the choice to introduce that player whenever they want no matter whether there's injury and then it creates a strategic aspect from a coaching and playing point of view. Because what this sub now creates is a whole series of headaches for everyone."

Beveridge said there were a range of issues that would develop from the medical substitute, including "turmoil" in the playing ranks and another challenge for under-resourced clubs after the more than $3 million cutback in the soft cap. 

"Not only do the decisions need to be made on the day, but then the doctors will have to substantiate whether or not a player can play the next week if there was an injury through administrative process that wasn't there before," he said.

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"And if we use our 23rd on Friday night as an example, if that player doesn't get called upon, he for his welfare won't be able to do a training session that night. 

"So we'll need to staff a training session on Saturday morning for that player, and with the soft cap cuts and everyone doing more than they ever have before, and then in the meetings of who [the substitute] may be, imagine the turmoil within the playing ranks as to who is that sub and does he miss out now on two or three opportunities to be in the team because he hasn't played? 

"There were so many considerations and I could keep going. From my point of view, it's disappointing a decision has been hasty and this is the course they went when there's so many other options that wouldn't have created the layers and headaches that this is going to create." 

Although it has been a coach-driven implementation, Beveridge said he was unable to attend the coaches' meeting with the League.

"I wasn't there and I had nothing to do with it," he said. "As you can tell by what I'm saying, I don't support it. Our staff and playing group are not sure because it's just been introduced out of the blue." 

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The Dogs haven't settled on who their substitute will be yet, although Norm Smith medalist Jason Johannisen appears unlikely to break into the line-up after being left out of the AAMI Community Series clash with Melbourne. 

Beveridge also backed recruit Adam Treloar to deal with the emotion attached with facing the Magpies for the first time since crossing to Whitten Oval.

"Adam seems to be on top of it. He's got through some injury and some physical battles in recent times and that shows he is, and it's not affecting anyone else to any detriment and that's always an important consideration," Beveridge said.

"We've just got to let that play out. I know as he's said it will be more of a relief after the game to play and probably get this one out of the way."