Villa have dropped into the bottom three for the third time this season and manager Lambert knows his side cannot afford to perform as they did in the first half.
He said: "We paid the price for starting too slowly. We just never got going in the first half. The second half, that's the way to play football.
"The first goal was really disappointing; the second goal, you sometimes can't stop them - it was a terrific strike - and then you are facing an uphill battle.
"But I couldn't fault them for the way they played in the second half. It is the first time I've seen a standing ovation when you've been beaten, especially at home.
"I just said to the players 'you can't play like that in the first half and turn that performance in during the second half'.
"It is sometimes easier to play when you are 2-0 down because no-one expects anything then. You've got to start like that - and we never started."