Roberto Mancini refused to blame goalkeeper Joe Hart for damaging Manchester City's title challenge as the champions slipped to a shock 1-0 defeat at Sunderland.
England midfielder Adam Johnson claimed the only goal against his former club to end City's eight-month unbeaten away league record.
Hart looked at fault as he was beaten at his near post by Johnson's 53rd-minute effort to leave City trailing seven points behind leaders Manchester United, who increased their advantage thanks to a late winner in a 4-3 victory over Newcastle.
However, Mancini's fury was directed at referee Kevin Friend rather than the England keeper, who was nevertheless at fault for allowing Johnson's cross to slip beneath him.
The Italian admitted his side had been "soft" in crucial areas, but also pointed the finger at the officials as City suffered a third consecutive defeat at the Stadium of Light, a venue where they are winless for almost four-and-a-half years.
Mancini insisted Friend and his assistants had enjoyed their Christmas Day celebrations rather too much, after claiming they missed Craig Gardner's foul on Pablo Zabaleta in the build-up to the decisive goal.
"Johnson was really clever because we all thought he was going to cross," Mancini said. "Instead, he shot. He did very well. I don't think Hart was at fault."
But the City manager was rather less positive about referee Friend, adding: "The referee ate too much for Christmas. He was not in good form.
"But that can happen after Christmas when they have a performance like that."
Mancini didn't spare his side from criticism. He said: "We didn't score and this is our problem. We just didn't score enough goals to win the game.
"Whenever we had chances, we were too soft. We were too soft in attack, too soft when we got chances, too soft when we shot.
"Sometimes we didn't shoot when we should have. We wanted one touch more and that's no good.
"When you play against a team like Sunderland, who defend with all their players behind the ball, if you get a chance then you need to score. They are a bit of a bogey team for us here. Maybe next year we won't come."
Although United now look firm favourites for the title, Mancini shrugged-off their seven-point advantage and said: "What happened at Old Trafford is not important to us. We know United are a fantastic team and will probably win every game, but the season is long.
"United are better than us at present, but it can change. They are on the top but we have the time to recover. Seven points isn't a problem."