Craig Brown lamented the loss of goals at Dunfermline in his team's 3-3 draw, a result that leaves Aberdeen only a point above bottom team Inverness.
"There's good team spirit and certainly good determination but we're careless and we concede goals very, very softly," said the Dons boss.
"The players are aware of that and it'll only come good with me and Archie Knox getting on to them.
"Certain individuals didn't perform their defensive duties properly."
Andrew Considine headed Aberdeen ahead in first-half injury time but they were pegged back by an Andrew Barrowman goal in 54 minutes.
And when goals by David Graham and Liam Buchanan put the Pars 3-1 up, and with Inverness level with Hearts, at one point the Dons were at the foot of the Scottish Premier League.
However, Hearts' subsequent 2-1 victory over Terry Butcher's side and a brave comeback by the Reds - an Alex Keddie own-goal and an 88th-minute Josh Magennis shot - saved Brown and his team from that embarrassment at full-time.
"When you go one up and having played reasonably well in the first half, it seemed inconceivable that halfway through the second that we'd end up 3-1 down," said Brown.
"We were far too complacent and slack at half-time.
"There must have been a misunderstanding in their heads after going into the lead just before the interval that it was just a case of going through the motions in the second half.
"That's unacceptable and they were told that in no uncertain terms.
"At 2-1 down Josh Magennis missed a great chance to equalise. In fact, he could have had three goals before he finally did score the equaliser.
"I think on chances created we probably deserved to win the game, a game that would have been good for the neutral spectator."
Brown ended his post-match interview by paying tribute to the travelling band of Aberdeen supporters.
"I think we owe that comeback to the fans who stayed behind that goal," he said.
"A half-dozen or so left but the vast majority stayed behind and cheered the team on.
"I keep saying to the players that I can't quite understand why they are so fortunate to get a support like this, particularly after some of the performances."