With the Red Devils leading 1-0 in their Premier League game against Tottenham on January 20, Wayne Rooney went down in the penalty area after appearing to be fouled by Spurs defender Steven Caulker but no spot kick was given, prompting the Scot to criticise the official's performance in his post-match observations.
The FA subsequently invited the United manager to explain his comments, which he did, and the governing body must now decide by Tuesday evening whether or not to charge the 71-year-old.
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"That is what I have put in my letter exactly but you know the FA.
"You never know. It is one of these things. We are high-profile."
The United boss suggested that the media had a huge part to play in the charges, with fellow Premier League managers Roberto Mancini and Harry Redknapp only being given warnings earlier in the season for similar offences.
"I think that is what you will find," he observed. "That is why they have sent me a letter."