Paul Lambert spoke of his immense frustration after seeing Southampton defeat Villa courtesy of a penalty that should never have been.
Lambert was deeply upset by Mark Halsey's decision to award a first-half spot-kick after television replays showed that Enda Stevens didn't touch Jay Rodriguez in the penalty box.
Lambert said: "I have seen it loads of times and had a chat with Mark after the game.
"He was adamant he was 100% right and he's guessed. It's never a penalty that, never.
"From our point of view, Mark has got it wrong. He'll be embarrassed by it, totally embarrassed.
"He's telling me he's 100% right. It's nowhere near it.
"I just think a referee in those big moments in big areas of the pitch, you have to get those right.
"There's no point guessing or surmising that something has happened. You have to get it right.
"That's where the let-down is. For Mark to say he's got it right? I am pretty sure he'll be embarrassed by it. I think Mark is experienced enough. He's been in the game a long, long time.
"He's a good referee. I just think in big moments in big games, you have to be right. You can't guess or surmise in the penalty area."
Despite the penalty, Lambert felt his side created enough chances to win the game, calling the second half performance "relentless".
He added: "Listen I can't fault them for that second half. They were relentless. We had loads of chances.
"There's a way to get beat and I couldn't fault them for the way they went about it in that second half.
"The crowd are right behind it. We couldn't do anymore than stick it in.
"You keep going. There's a long, long way to do. There will be loads of twists and turns in this whole thing.
"But in the second half I couldn't fault them for the way they went about it."
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