Andre Villas-Boas says Howard Webb cost Chelsea all three points and believes top referees should be in charge of the top games.
Chelsea raced into a 3-0 lead against Manchester United on Sunday but the visitors were awarded two penalties by Webb which were both converted by Wayne Rooney before Javier Hernandez grabbed the equaliser.
The penalty decisions by Webb, particularly the second one, left Villas-Boas fuming and he says United were gifted a route back into the game.
Branislav Ivanovic was adjudged to have brought down Danny Welbeck but the Chelsea boss says Webb and his officials got it wrong.
"The second penalty was very, very dubious," Villas-Boas said. "I don't know if Howard Webb had the correct angle to make the decision, maybe the linesman made the decision but it was very unlucky from him to give it.
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I'm not sure if he was compensating from anything in the first half, but it was the wrong decision.
It was a big disappointment, generally, on the way it happened.
"(It was) a dubious decision that, in the end, shifted the running of the game. We expect in top games to have top refs and at the moment it hasn't been happening for us."