Ange Postecoglou bemoaned Nottingham Forest's lack of killer instinct after he suffered his second successive defeat as manager with a 3-2 Carabao Cup third-round loss at Swansea City in the Carabao Cup third round.
The Premier League side had led their Championship opponents 2-0 but the Australian, who replaced Nuno Espirito Santo at the City Ground this month, looked stunned as Cameron Burgess fired in a rebound deep in stoppage time to send the home fans wild.
"I just thought it was a game we really should have killed off long before it got to the stage that it did," Postecoglou told Sky Sports.
"I got the sense we were getting a bit comfortable and thought the game would finish off easily but that's not what happens, particularly in cup football. I thought we scored a good third goal.
"I think the lads got a bit comfortable in that moment and you've got to know the warning signs. We had to finish them off and we had plenty of opportunities to do that, and a couple of decisions didn't go our way.
"Players just thought it would naturally finish that way and we've paid a heavy price for that. We need to improve."
Forest had controlled the opening half with Igor Jesus scoring twice - his first in the 14th minute when he fired in at the far post after a ball rebounded into his path and the second just before the break after a flowing move.
There was no hint of the drama to come for most of the second half on a rainy south Wales night but Swansea got a lifeline with just over 20 minutes remaining as Burgess found space to head in from a corner.
Slovenian substitute Zan Vipotnik then levelled in the third minute of stoppage time and Forest could not even get to a penalty shoot-out as Burgess pounced after Ethan Galbraith's piledriver came back off the woodwork.
Postecoglou's side have now conceded six goals in his two games after his Forest reign began with a 3-0 defeat at Arsenal in the Premier League on Saturday.