Rory Sloane's testimony and his extensive history of eye and facial injuries also helped save the Adelaide captain from a one-week ban.

But at the end of a marathon tribunal session on Tuesday night, Brisbane hard nut Mitch Robinson was found guilty of forceful front-on contact and his one-game suspension stands.

While Rioli is free to play against North Melbourne and Sloane will take on Collingwood this weekend, Robinson will miss the Lions' match against Essendon.

Rioli was facing a one-game ban for cannoning into Gold Coast young gun Matt Rowell as they contested a mark.

Rioli's advocate David Grace QC used the example of Riewoldt, who fearlessly ran with the flight of the ball and collided with a group of players when he took his mark against Sydney at the SCG.

He said if Riewoldt had not taken the mark and collided with an opposition player, would that have meant the Saints legend was guilty of rough conduct?

The tribunal deliberated for more than 30 minutes before deciding in Rioli's favour.

The Eagles successfully argued Rioli was going for the mark before bracing for contact at the last moment and he was cleared even though they didn't convince the tribunal the contact to Rowell was not high.

"Incidents such as this, where the question revolves whether and how the player is contesting the ball, are not easy," Gleeson said.

"This tribunal will be astute to uphold any charge where a player was initially intending to contest the ball, but changed that intention and in doing so, breached his duty of care.

"That is not this case."

Sloane successfully argued his charge of making contact to the eye region of Fremantle utility Blake Acres should be downgraded from intentional to careless.

That meant his penalty went from a one-game ban to a $2,000 fine.

Tribunal chairman Jeff Gleeson QC referred directly to Sloane's evidence when explaining the jury's verdict, saying they believed him.

He added several other factors also went in favour of the Adelaide player, including his awkward position after tackling the Dockers player.

Acres also didn't suffer any injury in the incident.

The Crows acknowledged the incident was low impact and high contact, but were adamant it was not intentional.

In his evidence, Sloane detailed his own history of facial and eye injuries because of football, including a detached retina last year that had the potential to end his career.

"There's no way I'd go after anyone's eye because I'm very aware of the damage it can cause," he said.

"I was super close to being finished in football and close to losing my eyesight so there's no way I'd go near anyone's eye."

But Brisbane failed to convince the tribunal that Robinson's contact with Port Adelaide's Xavier Duursma was reasonable.

Duursma suffered a collarbone injury and is no certainty to play in round two.

"The risk to Duursma should have been obvious to Robinson, who could and should have avoided head and neck contact ... he breached his duty of care," Gleeson said.

St Kilda defender Dougal Howard is challenging his $3,000 fine for rough conduct against Collingwood ruck-forward Mason Cox with a written submission to the tribunal.

Australian Associated Press