Their hosts had won only one of their last ten games and had recorded just two Premiership wins in front of their own fans in 11 months. They kicked off last night one point above the play-off place.
Perhaps it is the artificial surface at the Superseal Stadium which does not appeal to Aberdeen, who have now won only once on their last five visits.
Not that the home fans were complaining. This shock result hoists them, albeit only until tonight’s matches are completed, into the top six.
Hamilton were very much the underdogs here but someone forgot to tell Martin Canning’s side, who set about the Dons with relish straight from the kick-off. Even so, the long-suffering home support were as surprised as anyone when Accies took an early lead.
There appeared to be little danger imminent when playmaker Ali Crawford chipped the ball towards Alejandro D’Acol. The Brazilian had his back to goal and was short of support but Anthony O’Connor suffered a rush of blood to the head and pulled him to the ground.
D’Acol picked himself up and drove the resulting penalty kick low to the goalkeeper’s right to claim his fourth goal of the campaign.
Aberdeen were all over the place during the opening ten minutes. D’Acol then fired a shot into the side netting while Joe Lewis had to dive to his left to beat away a 25-yarder from Darian MacKinnon.
It took the visitors 27 minutes to see the whites of Gary Woods’ eyes and, when they did, Jonny Hayes fired his angled drive down the former Ross County keeper’s throat.
At least they had gained a foothold in the game, although Hamilton were giving as good as they got and, in the case of MacKinnon, sometimes rather more than that.
Mark Reynolds had an opportunity to equalise five minutes from the interval but directed his header from Hayes’ free-kick into Woods’ arms. However, the central defender was fortunate not to score an own goal with a careless back-header which bounced inches wide of Lewis’ right-hand post.
Aberdeen sought a penalty when they claimed a handball against MacKinnon, when Shay Logan went down following a coming together with Michael Devlin and again when Wes Burns went to ground under pressure from Greg Docherty; referee Willie Collum and his assistants were not inclined to agree.
McInnes, pictured, made a triple substitution after 64 minutes in a desperate attempt to rouse his team from their torpor but they still lacked inspiration and Lewis needed two attempts to gather a venomous drive from Docherty.
Aberdeen tried to get behind their opponents on the flanks to no avail and they had no more success when they attempted to play through the middle. Whether going short or long, they foundered on the rock of an Accies rearguard which had been breached in ten of their last 11 fixtures. Indeed, Lewis prevented Hamilton from extending their lead when he saved a shot from Grant Gillespie after Crawford had back-heeled the ball into the midfielder’s path.
Even four minutes of stoppage time was not sufficient for McInnes’ men to salvage a point and, in truth, they did not deserve one. A draw would have flattered them. As it was, Hamilton’s players enjoyed the rare experience of being applauded from the field at the final whistle.