Villa will face Chelsea in the Carling Cup tonight.
O’Neill said: “Are Chelsea harshly treated? No. Referees are not setting out with a vendetta towards Chelsea.
“Sometimes there is a view that if you are trying to highlight something to a referee a day or two before the next game, you are inclined to try to put that pressure onto the referee for the next game.
“I wouldn’t want the ref to feel that, because Chelsea feel they have been harshly treated in a previous game, that they start to become lenient.
“You referee the game as you see it. If their best is as genuine as they can do, then I don’t think you should have any severe criticism of them.”