Mark Clattenburg's explanation of Wayne Rooney's clash with James McCarthy will determine whether the Manchester United striker is banned.
Wigan boss Roberto Martinez was incensed by the sight of Rooney's elbow connecting with the side of McCarthy's head and sought out Clattenburg for an explanation at half-time.
The Durham official told Martinez he felt there had been "a coming together", something he appeared to indicate through hand gestures at the time.
That cut little ice with the Latics manager, who felt the decision was straightforward, a view endorsed by Match of the Day duo Alan Hansen and Mark Lawrenson when they analysed the incident.
The only obvious way round this for Clattenburg when he sends in his official match report would be to state he saw the clash, but not the elbow.
Even then, the FA would be within their rights to ask exactly why he gave the free-kick considering, without the elbow incident, McCarthy had moved towards Rooney rather than the other way round.
If Clattenburg says he saw the entire clash fully, Rooney is likely to escape sanction, although a three-match ban could see him miss this week's Premier League games with Chelsea and Liverpool, plus the FA Cup sixth-round tie against either Arsenal or Leyton Orient.
Sir Alex Ferguson's initial reaction was to steel himself for a media backlash, which duly arrived from Hansen and Lawrenson.
"Every picture tells a story and sometimes you can't defend the indefensible," Lawrenson said.
And Hansen added: "He (Rooney) is in big trouble. You can't argue with the pictures.
"There is some conjecture about whether the referee saw the incident or not. Is he looking at the ball? Categorically, he is not looking at the incident. He is looking at the ball.
"McCarthy takes a step to his left to try and block Wayne. He (Rooney) swings the elbow. He has thrown the elbow, smacked him on the head and should have been off."
Should Clattenburg leave the FA free to launch a charge, which under the new fast-track process could be dealt with before kick-off against Chelsea even if United opt to appeal, United are bound to raise accusations of double standards.
Although Newcastle's Mike Williamson was charged with violent conduct following a clash with Johan Elmander at St James' Park earlier this season, there are other instances of players not being hauled over the coals.
Nigel de Jong and Liam Ridgewell - coincidentally for a tackle on McCarthy - both escaped further sanction for bad challenges during 2010, whilst Steven Gerrard got away with flicking a 'V' sign towards Andre Marriner at Wigan last term.
Ferguson ripped into Michael Ballack when the German elbowed Patrice Evra during the 2009 Community Shield at Wembley, but again the incident was not punished further.
The United boss has already suffered in his dealings with Clattenburg, having been handed a £5,000 fine and two-match touchline ban for a half-time outburst at the official at Bolton in 2007, when he felt Kevin Davies had overstepped the mark in a challenge with Evra.
As he left Wigan though, he appeared to be suspicious of the part media reaction might play in Rooney's situation.
"I have had a chance to see it," the Scot said. "There is nothing in it.
"But, what will happen, the question has been asked and because it is Wayne Rooney the press will raise a campaign to get him hung by Tuesday or electrocuted or something like that.
"It is unbelievable. Watch the press. It will be interesting to see it."
Ferguson's assistant Mike Phelan was not so aggressive in his views.
However, he believed Clattenburg dealt with the matter at the time.
"I don't know whether there should be a witch hunt," he said. "The referee saw what he saw and he kept the game rolling.
"We can't dispute a referee's decision. He is out there on the field to take charge of the situation."
