BRISBANE Lions coach Leigh Matthews has questioned the AFL's new interchange system, and believes the league is complicating a "very simple" concept by appointing official stewards to oversee bench proceedings.

Matthews said the changes, which have seen the creation of a holding area around the interchange gates and the introduction of officials to enforce one-for-one rotations, seem unnecessary and will incur a "severe" penalty if breached as of next weekend.

"It's a very complicated system to get the end result," Matthews said, after the Lions trialled the changes for the first time against Carlton on Saturday night at Telstra Dome.

"I can understand interchange players being in a little box because that clears the space between that and the boundary line for the boundary umpires. I can understand that.

"But, if you've got an AFL interchange steward who sits there, to simply make sure you're got 18 on and if you get more than that, he tells the emergency umpire and you get a free kick against you.

"I never could quite work out why an interchange steward has to be told an interchange is going to take place. What does that do?

"It seems to me to be a very complicated system to get a very simple end result of making sure you've only got 18 at any one time."

The new rulings have been made to eradicate the chance of more than 18 players ending up on the field at one time, after the North Melbourne-Sydney Swans draw in round six where the Swans were found to have a 19th man on the ground in the dying moments.

The Lions were a man down for a period during Saturday night's game when there was confusion surrounding a Jed Adcock interchange as the steward went about recording who was to replace the midfielder as he came off.

Matthews said such a "technical" error is not worthy of a 50m penalty, which is almost certain to result in a goal to the opposition.

"If you make the technical mistake and say Jed comes off and a player goes on, and that wasn't the player that the interchange steward had was going to replace Jed, next week I'm told that's the free kick, 50m penalty, automatic goal," he said.

"You can get severe penalties for a technicality. If you've got 19 on the field, it should be a severe penalty and you should get all that stuff.

"Is there any particular reason for anyone else, apart from the clubs … as long as you've got the same jumper on and there's four sitting on the bench and 18 out there … anyway.

“I think the people that are running the interchange bench will be on stress leave very quickly."

Matthews also said he can't understand why the rotations are set to be recorded in such depth by the league.

"I don't think [the data] goes anywhere; I don't think it's part of a big picture research project," he said.

"There might be a reason, but I just can't sort of fathom why you even have to check with an interchange steward before you make an interchange."

And, he said the Lions will look at putting an extra staff member on the bench to ensure the club does not infringe the new rules as of next round.

"I think most clubs will because the penalty for putting the wrong bloke on at the wrong time is severe," he said.

"I know the system but I'm not quite sure I've been made aware of why this system needed to be implemented."