Andy Robinson believes his Scotland side have themselves to blame for the defeat by Argentina that could cost them a World Cup quarter-final place.
The Scots appeared to slacken off after going 12-6 ahead with 10 minutes to play in their Pool B encounter as Lucas Gonzalez Amorosino scored a try.
"We had complete control of the game, but one slip of concentration cost us," said the coach after the 13-12 loss.
"First, to lose the restart, then secondly a poor defensive lapse."
Robinson believes his side ought to have secured a win that would have ensured qualification for quarter-finals.
"We played well second half, but you've got to finish sides off," he said while praising Argentina. "One slip-up and it is seven points.
"Credit to them, they were under a lot of pressure, but they have fighting spirit.
"You saw what it meant to them to win this."
Argentina also defeated Scotland in the quarter-finals of the last World Cup and Robinson said the loss in Wellington had hit his side hard.
"The dressing-room is absolutely devastated," he revealed.
"One lapse, 30 seconds of concentration, has cost them a Test match."
Scotland captain Rory Lawson was left to lament Lucas Gonzalez Amorosino's winning try.
"Ultimately, it was going to be small margins that dictated the winner tonight and, fair play, Amorosino took his try exceptionally well," said the scrum-half.
"On a night like tonight, it was always going to be about controlling territory, controlling possession and building pressure and they maybe just won that contest."
Scotland, who claimed a losing bonus point and are now level on 10 points with Argentina, must now beat Pool B leaders England to have any hope of progressing to the knockout stages.
That is because the Argentines are near certainties to defeat Georgia.
"We've got a six-day turnaround now, so we'll go away and look at the game," added Lawson.
"Ultimately, we've got to go to Auckland, put on a big performance, finish strongly and give ourselves a chance of progressing."
Argentina number eight Juan Martin Fernandez Lobbe, who is set to undergo a scan on his injured knee on Monday, said: "The dream is still alive so we're very happy.
"We'll keep on fighting until the end and today we got the reward, so we're very happy."
The former Sale Sharks back row also thinks Scotland can progress at the expense of England.
"I believe in this World Cup anyone can beat anyone," he said. "And the passion Scotland has and the way they play it's going to be a very interesting match on Saturday night."