Johan Mjallby has insisted that Celtic will not be derailed in their quest to land only the fourth Treble in their history by the threat of further referee blunders.

Whistler Don Robertson is set to be behind the goal at Hampden on Sunday afternoon in his capacity as an additional assistant at the William Hill Scottish Cup semi-final against Rangers, and Mjallby has no issue with that.

Robertson awarded Ross County a penalty after a clear Alex Schalk dive in Dingwall at the weekend before sending Scott Brown off for a lunge on Liam Boyce, who converted the kick. The referee also irked the Hoops support earlier in the season when he failed to penalise Motherwell player Ryan Bowman for a dangerous challenge on Kieran Tierney at Celtic Park.

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Ronny Deila’s Celtic lost the Scottish Cup semi-final two years ago to Inverness as they chased a Treble when a handball by Josh Meekings on the line stopped a Leigh Griffiths header going into the net as Celtic led 1-0.

Mjallby, though, doesn’t buy into the theory that Celtic are up against the officials as they look to perform a clean domestic sweep.

“You get some decisions for you and some decisions against you,” said the former Celtic defender and assistant manager. “You can’t look at it that way. The officials do everything they can to make everything right but it is impossible otherwise you would just have computers there making all the decisions. It is just the way it is.

“I am quite sure no-one in the Celtic camp will be thinking that way. I have never experienced that where you would walk around thinking that a referee was going to make a decision go against you and it will blow up your chances of winning a Treble.

If it happens it happens but that is not in your mind and it won’t be on Brendan Rodgers’ mind or the players’ minds. They are going out to play the game and even if they win the game on Sunday they still have another game to go.

“Of course it is fine [Robertson involved on Sunday]. He is a referee. I don’t know how many years and how many games he has been refereeing but he is there and has been appointed to do his job and I am sure he will do his job to the utmost of his ability.”

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Mjallby has also counselled caution ahead of Sunday’s meeting against Rangers at Hampden.

“Looking at the season, you have to say Celtic are favourites - not only for Sunday’s game, but to win the trophy which will mean they win the treble,” he said.

“They have had a wonderful season. Their confidence is sky-high. They have the right tempo, a lot of players are positive and have improved since Brendan Rodgers came in the door.

“But the last Old Firm game was a draw and we all know what can happen in these fixtures. Rangers will be confident they can raise their game and give Celtic a very hard afternoon.

“The new Rangers manager hasn’t changed too much yet, he’s just in the door, but they look to be quite solid in the few games they have played under him so far. They will need to be very solid defensively to have any chance of winning game on Sunday.”