Aston Villa boss Martin O'Neill was fuming with referee Phil Dowd after Manchester United won the Carling Cup Final at Wembley.
Controversy surrounded a penalty awarded to Villa in the fourth minute when United defender Nemanja Vidic brought down Gabriel Agbonlahor.
James Milner scored from the spot but referee Dowd failed to give Vidic even a yellow card, even though he was the last defender and Agbonlahor was through on goal.
O'Neill said: "It was plain for all to see. It was an inexplicable decision. I don't understand it.
"It's a goalscoring opportunity. He's felled in the penalty area. It's straightforward from an otherwise fine referee who has got it wrong. It's as simple as that.
"In a couple of days it's forgotten. We're losing finalists in a fine game of football, but it's a major point in the game.
"We played some really great football, some great performances.
"But you can't keep a team like Manchester United at bay all the time and they came roaring back in the second half."
United were level after 13 minutes, Michael Owen sweeping home the equaliser after Dimitar Berbatov and Richard Dunne had tangled in the area.
Owen went off shortly afterwards with a hamstring injury, but his replacement Wayne Rooney scored the winner with a 74th-minute header.
O'Neill backed his side to recover from the disappointment and book another Wembley date in the FA Cup final.
"It's hard to take," he said. "I thought we played splendidly, particularly in the first half, and got in front.
"Manchester United got the equaliser but at half-time I felt we were very, very capable of winning.
"I'm disappointed for the team but they're resilient, they're strong, they're young and they'll fight back."
He added: "We felt we were capable no matter what side they played. We have to try and get back here again in May because it's a worthwhile journey."