The Aberdeen manager was angered by his players’ slack second-half performance as Motherwell inflicted a classic smash-and-grab manoeuvre on their hosts.
Kevin Van Veen scored twice in eight second-half minutes shortly after the interval as Aberdeen’s defensive woes returned to haunt them. Glass admitted it was “a setback”. Their recently improved record now stands at two wins in their last 14 outings.
The Pittodrie side drop out of the top six and face a tough clash against Dundee United at Tannadice after the international break.
““As a result, we got what we deserved,” said Glass. “They were two of the softest goals that you’re likely to see. When things go against us like that, we showed last week (v Hearts) that we can react, but we showed this week that we didn’t react in the right way. We didn’t produce the levels that we did in the first half and got what we deserved as a result.
“It’s a setback because we’re looking to build. We don’t want to step backwards at any point. You’ve got to kill games when you’re on top and we didn’t do that in the first half and we paid the price.
“It’s a setback because it’s three points we’ve left behind and Motherwell have jumped ahead of us with three points. That’s what it is and we’ve got to start looking at Dundee United now.”
Aberdeen had hoped to consolidate their recent better form against the Fir Park side, who conceded six against Rangers last weekend. They started brightly and should have been ahead at half-time but some familiar brittleness reared its head in the second-half.
“I think there is more than one individual error within it,” said Glass. “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.”