Brenden NelJohannesburg - International Rugby Board referees boss Paddy O’Brien has revealed that South African assistant referee Cobus Wessels made a “grave mistake” that led to him being removed as touch judge for this weekend’s Tri-Nations Test between Australia and New Zealand. Wessels was further removed from the referees panel for the Tri-Nations by the IRB boss in a decision which was accepted by SANZAR.In a rare break of protocol, O’Brien explained to NZPA that Wessels had made a massive mistake in recommending a yellow card for Australian winger Drew Mitchell in last weekend’s Test match between the Wallabies and All Blacks in Melbourne.Wessels flagged an off the ball incident where he said Mitchell had not used arms to tackle All Black captain Richie McCaw and later received a second yellow for unsportsmanlike behaviour, reducing the Wallabies to 14 men for the last 38 minutes of the game.Scrutiny of match footage not shown on the night revealed that ruling to be well wide of the mark, according to IRB referees boss Paddy O'Brien.New Zealander O'Brien told NZPA the alleged tackle by Mitchell on All Blacks captain Richie McCaw was at the minor end of the scale and Wessels had paid the price for his over-reaction."If anything, it's lucky to be a penalty," O'Brien said."McCaw offloads as he's about to collide with Drew Mitchell, who puts his hands out and pushes him away. So there's no way it's a yellow card offence."As a result of that, with the second yellow, Australia went without a player for almost 40 minutes and that just shouldn't have happened."O'Brien said Wessels also called an All Blacks lineout throw not straight late in the Test when it was clearly down the middle."Assistant referees, we encourage them to intervene in the game but they've got to get it right. There were two decisions made which we felt weren't up to the standard required."Cobus has been very understanding, he admits that he got it wrong and we're not going to hang him out to dry. He's got to go away and think about that, referee the Currie Cup and hopefully learn a lesson from it."Wessels, who will be the television match official on Saturday, will be replaced on the touch line by New Zealander Keith Brown.However South African fans will continue to question why O’Brien was not more harsh on the Irish refereeing trio of Alain Rolland, George Clancy and Allan Lewis for their mistakes in the Tri-Nations Tests involving the Springboks but so vociferous to censure Wessels. Rolland and Lewis were sternly defended by O’Brien when the Springboks complained and Rolland was even awarded the Tri-Nations Test in Pretoria between the Springboks and Wallabies.Meanwhile, O'Brien also defended the refereeing trend this season that has seen a proliferation of yellow and red cards, causing consternation from some teams and supporters.O'Brien said attention should fall on the actions of the players, not the officials."We make no apologies for it. We're very tough on dangerous tackles, especially tip tackles," he said."This is the shop window of rugby so we can't have third grade players running around in club rugby tipping someone in the air and putting them down with legs above the horizontal."And there's no excuses for the headbutting and the other things that have happened."However, O'Brien may have conceded that lock Danie Rossouw was unlucky in his yellow card and suggested officials overstepped on occasion."There are concerns that there have been a couple of yellows where the referees have been over-zealous. The game is still a contact sport so we just want the referees to be accurate when it comes to what is foul play and what is hard rugby."