City were only 1-0 up when a handball decision was given against Andreas Weimann, with Sergio Aguero converting the resulting penalty to spark the rout, but replays showed it was the wrong call and the handball had not occurred.
“I think it was really unfair, that’s not hit Andy Weimann’s hand, it's hit the Man City [player’s] head. How [the linesman] saw that I just don’t know,” said the Villa coach.
“We were having chances and Joe Hart kept them in the game.
“It might not have made a difference to the score line, but all you want is an even field to play in and I don’t think we got that.
“It was a big decision. I’ve always thought that in the big moments in big games you’ve got the make the right call and maybe the game was just a bit big for that linesman.
“He’s guessed, that’s exactly what he did and you can’t do that at this level in football.
“I think up until that decision we were in the game.”