Sydney coach John Longmire says younger teams are being disadvantaged by the new runner rules, following the Swans' heartbreaking one-point loss to Fremantle on Saturday night.

From 2019, runners are only allowed out on the ground after a goal has been kicked, and must leave the field before the umpire restarts the play.

Longmire says the AFL's more inexperienced sides are being found out by the new rule, and believes common sense should prevail in reversing the rule back to what it was.

"You don't have to be Einstein to work that out," Longmire said when asked if it has a disadvantage on younger sides during his post-game press conference.

"We've got young kids out there that are running around … trying to think about everything in the game, including just trying to get their hands on the footy, plus doing the rotations themselves and trying to think through some (tough) situations.

"It clearly is not going to change before the end of the year, so we just have to deal with it and make sure our players learn from it. And they'll learn from it pretty quickly."

Longmire wants to see it revert back to last season, when runners were used freely and could give out instructions at any point of the game.

"I'd love it to (be brought back to) what it was but I'm not sure (the AFL will) say they were wrong," Longmire said.

"I just hope some sanity prevails because coaches aren't there completely to ruin the game and when you've got a really young team, you'd like to be able to help them a bit."

Sydney's 22 that took on the Dockers were the youngest team of any side this round.