SYDNEY Swans coach John Longmire says interchange stewards and umpires need to have clearer communication before penalising teams for interchange infringements.

The Swans were forced to concede a goal after they were penalised for an interchange infringement in last Friday night's loss to Carlton.

The decision was later found to have been wrong as the Swans only had 17 players on the field.

Longmire says the stewards and umpires should have conversed and properly discussed the breach before awarding a free kick.

"If the steward had have got out of his chair and looked to the right, he could have made a quick count that there were enough numbers on the interchange bench and we could have got the message out to the central umpires, (so) no damage done," Longmire said on Monday.

"From my point of view, that's the best conclusion to come out of it. You need to make a 100 per cent sure it's the right decision, and there was plenty of time to make that decision."

The AFL conceded that the incorrect decision was made and the interchange steward was likely to be stood down for round seven.

Longmire said he was pleased to see the league admit its error.

"I think we've done pretty well to get out of the AFL what we've got out of them. I just want to make sure that going forward those things shouldn't have occurred," he said.

"If there was a level of discussion it would have prevented it. It's pretty simple and I hope that happens from now on."

Longmire's side will be without 2010 best and fairest winner Kieren Jack for up to six weeks after he injured his right ankle in Friday night's match.

Jack had been tagging Carlton captain Chris Judd until he injured the ankle in the second term. He eventually returned to the ground but was on crutches in the rooms after the match.

"It's obviously disappointing for Kieren. I think he was getting back into some really good form. His first quarter on the weekend on Judd was excellent," Longmire said.

"He can play those roles and play offensive roles as well. It's disappointing for the team, but we make sure we get someone else in to replace him and get on with the job."