Sydney coach Paul Roos says he has no idea how to teach his team to tackle legally after events of the last couple of weeks.

Ruckman Shane Mumford was suspended for two matches after being charged with a rough conduct offence on Geelong's Gary Ablett who nonetheless recovered from the challenge to be widely considered the best player on ground.

Sydney contested the charge and although the AFL jury revised his conduct from reckless to negligent, Mumford's suspension was not reduced.

A week earlier, Sydney midfielder Ryan O'Keefe suffered concussion after his head hit the ground following a tackle, but no Brisbane player was charged.

"We saw some more tackles on the weekend, it's such a grey area," Roos told reporters on Monday.

"To be perfectly frank, I've got no idea how to teach my team to tackle.

"We just hope that the way we practice and the way we think the players should do it, that's all you can do."

Roos was clearly bemused by the judgment against Mumford, though he wasn't openly critical of the decision.

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

"We are certainly in a unique environment in AFL football."

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