Boss Stephen Glass accepts Aberdeen were punished for poor defending as their mini-revival was derailed by Motherwell.
Aberdeen lost 2-0 to the Steelmen at Pittodrie despite dominating possession and firing in 18 attempts at goal.
In contrast ‘Well mustered just two shots at goal – and netted with them both as Kevin van Veen bagged a second half brace.
It stopped Aberdeen’s resurgence in form having taken seven points from the recent triple header against Hearts, Rangers and Hibs.
Glass insists the defense switched off and showed poor awareness for both goals as Aberdeen crashed to a defeat that sent them back into the bottom six of the Premiership.
He said: ” I think there is more than one individual error within it.
“It is switch offs, it’s not reacting right.
“It’s poor defending and poor awareness and it’s poor willingness not to get beat.
“Pure and simple.
“If we do the professional thing in the second half, I think we come out winning but we didn’t so we didn’t deserve to win.”
‘No excuses, we didn’t defend well enough’
Aberdeen dominated the first half but had nothing to show for it.
They went a goal behind in the 50th minute when the defence switched off to allow van Veen a free shot at goal.
Van Veen doubled his tally seven minutes later to secure a win that leapfrogged the Steelmen above the Dons in the table.
Glass admits he was surprised at the poor level of performance after the break, particularly after last weekend when the Reds completed a second half comeback to beat Hearts 2-1.
He said: “It was a surprise after everything we were in the second half against Hearts last week when we came out and really dictated that half.
“It was the flip side this week and that’s the frustration.
“For 10 minutes we were second best and we paid the price.
“You have to do more to make it your day which we didn’t.
“No excuses, we didn’t defend well enough and found ourselves on the back of losing two goals and it’s then difficult to get back in.”