St Kilda's Brent Guerra's hot Wizard Cup form must cool for three weeks after he was rubbed out by the AFL tribunal.

Guerra was banned for rough play against Geelong's Cameron Ling in a heavily-publicised collision at the start of last weekend's Wizard Cup grand final.

The ex-Port Adelaide player ran off the edge of the centre square to lay a heavy head-high bump on Ling, who was being grasped in a tackle.

Tribunal chairman Brian Collis said the contact was "dangerous" and "reckless in all the circumstances", saying player must be protected when contesting the ball.

"We regard it as a serious offence. We think the potential for injury is significant and it's dangerous," Collis said.

Collis took account of Guerra's history of having not been previously suspended in a 65-match career.

Ling claimed momentary memory loss after the incident, but told the tribunal he had suffered no lasting injury.

He left the field bleeding from the cheek soon after another collision early in the first quarter.

Guerra pleaded not guilty to the charge and said he considered the bump to be fair because he believed Ling was in possession of the ball.

He had been instructed to run straight to the ball in the centre square.

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