Nemanja Vidic will get at least a one-match European ban following his dismissal in the FIFA Club World Cup Final.
Vidic was red-carded after raising his elbow into the face of Liga Deportiva Universitaria's Claudio Bieler four minutes into the second half of United's 1-0 win.
United manager Sir Alex Ferguson admitted referee Ravshan Irmatov had little option other than to dismiss the Serb.
The matter will be analysed by FIFA, with their findings then handed on to UEFA for action as they were the ones whose banner United were competing under.
If Vidic, who opted not to speak after the game, is ruled out for one game he will miss the away leg of the Champions League last-16 clash with Inter Milan.
Should the incident be deemed as violent conduct, he will be sidelined for both matches, plus the first leg of the quarter-final if United advance.
"We have been informed if there is a suspension it will be European Cup," said Ferguson.
"It was a soft sending off. But it depends how FIFA interpret it and how UEFA act in terms of the information they get.
"He didn't swing an elbow but he gave the referee no chance. He was correct to produce the red card.
"Vida is disappointed but he gave the referee no option.
"We were in a comfortable situation too. The two centre-backs were having their easiest game for weeks."