Sir Alex told MUTV: "It's absolutely ridiculous. I just cannot explain that decision. Managers get sacked on the basis of things like that. And he's going to referee a game next week? It's ridiculous.
"We're out and you could look at a lot of things.
"We missed a lot of chances for one, but the refereeing performance… Keith Hackett (of Match Officials Board) has got a lot to answer for. He's not doing his job properly.
"He should be assessed like everyone else. Martin Atkinson will referee next week, no problem. But his performance today should not be accepted in our game. I agree with Sepp Blatter, the standards here as opposed to the Continent is behind Europe. It's a big problem."