Paul Lambert was unhappy with the defending for the Fulham winner as his Villa team went down 2-1 late on in B6.
Lambert felt his team should have seen the game through in the closing minutes after coming from behind to equalise.
He said: "It was tough to take.
"Their winner was a poor goal from our point of view. You can't let someone put a ball into the box and then not be tight in the penalty area.
"We made a mistake with Westy where he tried to play a pass. That was the first error and the second error was not getting tight in the penalty box. That was what led to the goal.
"I thought it was too open. The injuries we had, with seven minutes to go, you take the point.
"You have to see a game through.
"You lose a goal and then get back into it. You have to see a game through. That's the big thing. They are young lads, yes, but they have to see the game through."
The defeat was Villa's 10th home league loss this season and Lambert accepts that addressing the form in B6 is a priority in the closing weeks of this season - and next term.
He continued: "We can't keep doing this.
"You have to rectify your home form, no two ways about it.
"The away games have seen our best performances. You can't keep losing at home.
"It's a big club with a massive fanbase. If you don't perform, they let you know."
Lambert was pleased with the display of Grant Holt, as he spoke of the mood of the forward he replaced - star man Benteke.
He also revealed why central ace Delph missed the match.
He added: "I thought Grant led the line great for us. He scored a good goal for us - a good header.
"We lost Fabian this morning which was a big disappointment. He trained yesterday. He was a bit sore. He was sore at the back of his legs. I think he will be alright next week. It would have been a risk if he'd played. He might have pulled something.
"Gabby hadn't recovered from the bug. Then you throw Karim in too and that's a big chunk of our team missing.
"It gave other lads an opportunity and to be fair to them, they acquitted themselves well.
"But as I said, the game was too open at 1-1. It was really open.
"In terms of Christian, no-one knew the extent of the injury so we had to wait and see what it was. It might have been just a strain but we weren't sure until he went to hospital on that day.
"I spoke to him yesterday. He's feeling okay. Whether that's the feeling of shock?
"When he gets the operation, he knows he will miss the World Cup. But I am pretty sure he will have other chances.
"He's in a generation for Belgium where you think they will qualify for another few tournaments."
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