The full-time whistle was met by boos from the travelling contingent as the Dons fell to a 1-0 defeat at the SMiSA Stadium courtesy of an excellent Connor Ronan goal.
Aberdeen dominated the ball with 68 per cent possession but mustered just one shot on target with a somewhat error-strewn performance. Despite a bright start to the second half, they never looked like breaking down a solid and organised Saints rearguard.
The loss saw Glass’ men miss the chance to jump to fourth in the table and are now just three points ahead of the Buddies in the table.
“It wasn't good enough – the creativity in the final third wasn't good enough,” the Dons boss said.
“It was disappointing. It was a poor performance. One moment of quality wins it for St Mirren and it's disappointing with the possession we had that one of our players didn't do it.
“In the first half we were the ones asked to make the running in the game and we didn't do enough with the possession.
“Second half we gave away a cheap goal from our point of view. It was a brilliant finish but we didn't do enough to threaten and you get what you get.
“We knew we'd jump a couple of places with three points. There aren't many games when we don't score in so that's disappointing, especially the amount of possession we had. Especially off the back of the run we've just had when the boys were feeling good about themselves.
“We need to make sure the boys are on board again now.”
"It's important we start picking up points on the road,” Glass said.
“A certain amount of mental toughness is required so if you don't win a game like that then you don't lose.
“Afterwards we talked about our quality when we’ve got that amount of possession and being harder to beat when we give the ball away cheaply.
"The boys aren't happy, nobody is, but we have to put that right on Saturday.”