SYDNEY Swans coach Paul Roos says he has no idea how to instruct his players to tackle their opponents following ruckman Shane Mumford's two-week suspension for rough conduct.

Mumford received a two-week ban after a vigorous tackle against Geelong, in which Cats star Gary Ablett was thrown to the ground and left dazed.

The Swans took Mumford's case to the tribunal where it was downgraded from reckless to negligent, but the big ruckman still received a two-week suspension.

A clearly frustrated Roos said he couldn't understand why Mumford was penalised against the Cats, but no Brisbane Lions player was suspended for the tackle that left Ryan O'Keefe concussed at the SCG a week earlier.

"We had Ryan O'Keefe who got knocked out at the SCG [against the Lions] and it's pretty hard to explain to him why," Roos said on Monday.

"We saw some more tackles on the weekend. It's such a grey area. To be perfectly frank, I've got no idea how to teach my team how to tackle. We just hope to practise the way we think the players should do it and that's all you can do."

Roos said he hadn't approached the League's umpiring director Jeff Gieschen for clarification of the rule and intimated that it would be a pointless exercise.

"Jeff doesn't look at the video and review the video. The umpire in that particular game deemed that a legal tackle," he said.

"We're in uncharted territory where you can make a legal tackle, where a player can get up and go to the next contest, have the next centre bounce clearance and go on and be clearly best on ground and have a player sitting on the sidelines for two weeks.

"We're certainly in a unique environment in AFL football."