Jim Goodwin reckons Aberdeen paid the price for key moments going against them once again after losing to Rangers at Hampden.
The Dons were denied a place in the Viaplay Cup final as Ryan Jack and Kemar Roofe netted to cancel out Bojan Miovski's strike.
A red card for Anthony Stewart was costly for Goodwin's side and it proved to be another tough one to take for the Irishman.
Goodwin said: “I could rhyme off the results since after the World Cup break, but I don’t think lack of character or lack of professionalism was the problem. It was key moments in certain games which cost us.
"One lapse in concentration, and a great strike from McGregor, kills us against Celtic. In the Rangers game we were 2-1 up and we conceded two sloppy goals in the seven minutes of injury-time which were added on.
"I don’t think the poor results have reflected some of the performances to be honest with you. The previous two league results? We kept two clean sheets.
"We should have beaten Ross County, we beat St Johnstone and we were feeling good about ourselves going into the game on Sunday.
"We really believed we could win the game and that was the big positive for me – we went to Hampden with confidence in ourselves and in the group that we could progress."
Aberdeen will now turn their attentions to the trip to Tynecastle on Wednesday night for a huge fixture with Hearts in the race for third spot this term.
Striker Duk was replaced by Jonny Hayes just after the hour mark against Rangers and faces a fitness fight to be fit for the Gorgie clash.
Goodwin said: “After about 20 minutes he started to feel his calf. We just tried to get him through it as best we could. Hopefully there is no long-term effect there.
"But we have got a number of the players who have cramped up and have muscle issues. Hopefully none of them are too serious.
"But the medical team are going to be very, very busy to turn them around in time for what is going to be a challenging game at Tynecastle on Wednesday.”
