Sir Alex Ferguson has rounded on the "idiots" who criticised David de Gea following the mistake that allowed Tottenham Hotspur to draw with Manchester United at White Hart Lane last Sunday.

Gary Neville and Alan Hansen were two of the more prominent critics of the Spaniard. Neville, a former United captain, spoke on Sky Sports on Sunday and Monday about how the goalkeeper's error had cost United two points, while Hansen used his newspaper column to claim that De Gea should be dropped if he makes another mistake.

Asked what Ferguson, whose team host Fulham in the FA Cup fourth round on Saturday, thought of the general criticism, the United manager said: "I am not getting into that at all. You have to listen to some idiots in the game."

When Neville's criticism, specifically, was put to him, the Scot said: "It is better we deal with David de Gea rather than the press deal with him. We are quite good at that. He had a fantastic game and was 30 seconds away from that. It is unfortunate for the lad but he has to deal with it. We will help him. Outfield players maybe make 20 mistakes in a game. But they [goalkeepers] are in a crucial position. We are OK with him. I thought we should have had a foul in the buildup to the goal. Rafa [da Silva] was fouled going out to the touchline. [Clint] Dempsey fouled him. The ball goes back to the left full-back and he bumps it into the box and it is a goal."

Ferguson also claimed that the Football Association had been panicked into reacting to his comments about the match officials against Tottenham because of who he is.

Ferguson had said the linesman Simon Beck had a "really poor game" and added: "I'm disappointed with him. We have not had a good record with him," which was a reference to the assistant failing to flag Didier Drogba as offside as he scored Chelsea's winner in a crucial victory during Chelsea's title win in the 2009-2010 season.

Asked if he had been merely giving an opinion, Ferguson said: "That is what I have put in my letter exactly. But you know the FA. You never know. It is one of these things. We are high profile. I think the press play its part too. They panic when the press … Some of the headlines were: 'Ferguson may be charged by the FA.' You have your part to play in that because the profile of me is such that the FA naturally panic as soon as the press criticise them. That is what you will find. That is why they have sent me a letter. There is no doubt about that. Whether I think it is unfair or not doesn't matter to them really at this point. I just think it is more about me than what I have said."

Ferguson also refused to comment on Rafael Benítez again claiming that the United manager can influence the FA, following the Spaniard's infamous "fact" tirade when manager of Liverpool in 2009. "I'm not bothered about what Rafa says to be honest with you. I've got more on my mind," the Scot said.

Iker Casillas has been ruled out for up to 12 weeks after surgery to repair a fractured bone in the Real Madrid goalkeeper's left hand, putting him out of both Champions League ties against Manchester United. Spain's No1 suffered the injury during Real's Copa del Rey quarter-final second leg against Valencia on Wednesday when his team-mate Alvaro Arbeloa accidentally kicked his hand while trying to clear the ball.

Wilfried Zaha's move to United for an initial £10m should be sealed next week, after he passed a medical. Of Zaha, who will be loaned straight back to Crystal Palace, Ferguson said: "We like to sign young players with potential. We can develop players well, as we have proved many times. So hopefully the boy will enjoy it coming here. He's a winger, only a young lad, 20 years of age, so we will see."

Zaha added: "I am delighted to be joining Manchester United and ending the recent speculation. I would like to thank the owners at Palace for making the move possible. However, my focus for the next five months will be solely at Crystal Palace."