Nemanja Vidic was sent off for a second bookable offence just moments after Liverpool skipper Jamie Carragher had received just a yellow card for bringing down Michael Owen when the United striker had a clear run on goal.
"We didn't handle the atmosphere of the game, I thought," Fergie said after the game.
"We didn't handle the decisions against as well. We should have been better at that, we have got enough experience to do it.
"The second half we improved a good deal. But we lost out to one or two major decisions.
"The atmosphere is hard to handle for the referee. Whether he had enough experience, I don't know. He will certainly learn from it.
"The most controversial decision was Carragher bringing down Michael Owen. He was clear through.
"The laws of the game were altered to prevent professional fouls of that nature and if Carragher goes off, he is their best player and their captain. It would have been a different game. They would have been under pressure.
"The referee was only four or five yards from it he cannot use a covering defender as an excuse. Michael was clean through. With Michael's pace he is going to get away from him."