Boss Barry Robson has demanded Aberdeen learn from their costly defensive mistakes in the 6-0 mauling by Celtic.
The Dons’ recent positive momentum was stalled by the heavy loss to the Premiership champions at Parkhead.
Robson admits the Reds were “too open” to the point Celtic looked like “they could score every time” they attacked.
The Aberdeen boss was also frustrated at the injury time collapse when his team conceded three late goals in time added on.
It was a damaging defeat which left Aberdeen languishing ninth in the Premiership table, just two points ahead of bottom club Livingston.
However, the Dons have two games in hand.
Robson will demand an immediate improvement after the international break in Aberdeen’s next game – at home to Rangers on Sunday, November 26.
Robson said: “We have got to learn that you cannot leave yourself open.
“Once we lost that third goal you have got to have a structure and stay in the fight.
“But we just looked like we were too open and they could score every time.
“We need to learn that you cannot do that especially in an arena like Parkhead.
“You cannot go down to Parkhead and not be close to people and not perform.
“If you lose a goal you have to stick together and get close to each other – but we never did that.”
‘Not good enough all over the pitch’
Robson has faced Celtic three times away from home since taking over as Aberdeen manager in January. They have all ended in heavy defeats, with the Reds going down 4-0 in Glasgow in February and 5-0 in May.
Robson insists it was not only defensively where the Reds underperformed, saying it was throughout his team.
He also revealed details of his half-time team talk in the Parkhead dressing-room in a bid to resurrect the Dons in the game.
Robson said: “It was not good enough all over the pitch.
“We looked passive as the first half went on.
“We spoke to them at half-time and told them we need to get closer to players.
“That we need to try to force them back the way and get a better press on.
“For the first 15 minutes of the second half, we started to get to where we wanted to be.
“In the second half, we tried to get back into the game and then the penalty (to make it 3-0) swings it.
“After that you have to try to not lose more goals.
“In the 10 minutes that were added on, they opened us up.
“We lose another one, then another and it wasn’t good enough. The players know that.
“We have to get a better structure about us and get stronger together.
“We lost three goals so you have to get organised and help each other – but we never did that.”
Another costly European hangover
Aberdeen’s heavy defeat at Parkhead came less than 72 hours after they drew 2-2 with Europa Conference League Group G Leaders PAOK in Greece.
The Dons ended PAOK’s 100 percent record in the Conference League groups this season.
However, the demands of the clash at the Toumba Stadium in Thessaloniki appeared to have taken a toll.
The Reds have struggled to balance Euro action this season with domestic commitments – despite an extensive summer summer transfer window rebuild.
Of the six Premiership games immediately after a Euro fixture this season, the Dons have won just once, drawing two and losing three.
Robson accepts full culpability for the hammering at Parkhead.
He said: “We have performed well in a lot of big games recently, but never performed against Celtic.
“I take responsibility as I am the manager of the football club.”