A Celtic source leaked that club officials had been in talks with the Scottish Football Association over perceived decisions going against the Hoops this season.[LNB]Both Old Firm games so far this term have seen key rulings go against Celtic, including several penalty claims in their 2-1 defeat at Ibrox in October, while Bhoys striker Marc-Antoine Fortune had a goal disallowed in the 1-1 draw at Celtic Park on January 3 for a foul on Rangers goalkeeper Allan McGregor.[LNB]The Bhoys are seven points behind Gers at the top of the table and the row has ensured that McDonald's decisions will come under the spotlight even more on Sunday.[LNB]But the Old Firm ref is adamant that there is no conspiracy against Celtic or a deterioration in refereeing standards - just greater media scrutiny.[LNB]"I treat every match the same in terms of preparation," said McDonald.[LNB]"You have to bear in mind the scrutiny and unique pressures of an Old Firm game but you cannot be overawed.[LNB]"You are aware it is the biggest game in the country and the TV coverage is much greater but you have the added aspect of phone-ins, websites and other media outlets.[LNB]"It is a constant feeding frenzy but, as Ally McCoist said recently, the refereeing and decision-making hasn't changed much - it's the exposure that is far greater."[LNB]McDonald has refereed over 200 Scottish Premier League matches and four Old Firm derbies, including last season's Scottish League Cup Final, which Celtic won 2-0, and Rangers' 4-2 league win at Celtic Park last term, when Jan Vennegoor of Hesselink and Gers' Daniel Cousin were sent off.[LNB]McDonald's comments were released on the SFA website after Hampden bosses made an angry response to the Celtic leak, which they feel was done in an attempt to put pressure on Sunday's officials.[LNB]"The important thing for referees is not to take the criticism to heart," said McDonald. "You have to learn from all experiences, good or bad.[LNB]"I have always had the respect of the players in these games, which I hope is the case on Sunday."[LNB][LNB] Rangers v Celtic. Click here to bet.