Sir Alex Ferguson blamed a string of refereeing decisions in favour of the opposition after Manchester United's 2-0 defeat at bitter rivals Liverpool on Sunday.
Goals from Fernando Torres and David N'Gog shot down the champions at Anfield, but afterwards Ferguson was unhappy with the performance of referee Andre Marriner.
Marriner sent off Nemanja Vidic midway through the second half, but opted to keep his cards in his pocked when Jamie Carragher felled Michael Owen soon after.
He also waved away a penalty appeal from the visitors when Carragher and Michael Carrick clashed in the box.
"It is very difficult atmosphere here. There was a wounded animal aspect to the game and it was something we did not overcome," said Ferguson.
"I think it affected our players and it affected the referee. There were so many controversial things that happened we have to feel aggrieved at some of them.
"The Vidic booking was the worst decision. It is a foul, fine. But the player has played on, he won the second ball and knocked it for a throw-in and got booked. It put Nemanja under pressure.
"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."