Wigan manager Roberto Martinez claims Wayne Rooney should have been sent off after catching James McCarthy in the face with his elbow during the opening minutes of Manchester United's 4-0 win at the DW Stadium.
The home fans were incensed but referee Mark Clattenburg took no action, apart from awarding the hosts a free-kick.
Having looked at the incident again, Martinez is convinced his side should have been playing against 10 men.
"I saw the incident clearly and the referee did as well because he gave the free-kick," said Martinez. "Once you give a free-kick it is quite clear that it is a red card. When you look at the replay, it is quite clear he catches James McCarthy in the face with his elbow.
"If one of my players had done that, I would think he was very lucky to stay on the pitch. It is a big call in the game. It is unfortunate because the referee saw it but he didn't feel it was a red card.
"It was not because he was Wayne Rooney. It was an incident in the game. That is it."