PORT Adelaide veteran Kane Cornes will miss Saturday night's clash against St Kilda after unsuccessfully challenging his rough conduct charge at the Tribunal on Tuesday night. 

Cornes could have accepted a one-game ban for his behind-the-play hit on Hawthorn midfielder Sam Mitchell, but he didn't risk an extra week by challenging, giving the Power a free swing. 

The veteran's six-year good record reduced the demerit points penalty from 225 to 168.75, but he will be a significant loss as the Power seek to strengthen their foothold in the top eight. 

The incident was assessed as intentional, low impact and body contact, with the Power challenging on the grounds that contact was negligible. 

"My intention was to check Sam Mitchell, let him know I was there and not let him run on and be involved in the next passage of play," Cornes told the Tribunal.  

"I intended to do that by a bump. It was just an ordinary bump."

Cornes, who ran with Mitchell in Saturday's clash, said a key part of his role was his work off the ball and he was "really surprised" his opponent went to ground. 

"He could see me coming and that's why he disposed of the ball, then he took two steps back," Cornes said.  

"He would have known exactly where I was and he would have known I was coming towards him.

"I was really surprised he went to ground."

Cornes' counsel, Mark Griffin QC, argued contact was negligible and it was possible Mitchell was "milking the situation to secure a free kick or 50m penalty". 

The jury of Emmett Dunne, Wayne Henwood and Wayne Schimmelbusch, however, took four minutes to uphold the charge. 

Griffin then argued there were exceptional and compelling circumstances and the charge should be downgraded from a level two to a level one offence, reducing the starting demerit points from 225 to 125. 

He argued Cornes, who has played 260 games, deserved "greater consideration than your average player" based on his 13-year career without being charged with an offence. 

West Coast ruckman Dean Cox is the only current player to have played more games and maintained a clean record. 

The jury deliberated once more, but returned after seven minutes and concluded there were not compelling and exceptional circumstances. 

Tribunal counsel Andrew Woods said a clean record should be expected of players, not treated by the Tribunal as something exceptional and compelling.     

Nathan Schmook is a reporter for AFL Media. Follow him on Twitter @AFL_Nathan