Daniel Hourcade rued the 10-minute lapse in concentration that saw Argentina beaten by South Africa in their opening match of the Rugby Championship.
With 70 minutes played in Nelspruit, the Pumas had a 10-point cushion after Nicolas Sanchez had converted Santiago Cordero's try, the score standing at 23-13.
South Africa were not to be denied, though, as they launched a dramatic comeback to win 30-23.
Tries from Johan Goosen and Warren Whiteley plus two conversions and a penalty from Elton Jantjies secured victory for the Springboks, leaving Hourcade frustrated his side had missed a glorious opportunity.
"We controlled the game well for 70 minutes and in the last 10 made some mistakes, we lost control and that was it," said the Pumas coach.
"We made mistakes that cost us the win. Matches last 80 minutes and we could not close it."
Hourcade was pleased with his side's defensive play apart from the late collapse, blaming the wet conditions for their last-gasp defeat.
"We had a solid defence that pushed hard on key players and did not let them generate the game they wanted to. We were good in the breakdown and defence, our key weapons," Hourcade added.
"The ball was difficult and slippery, so we could not try much more than we did. It was generally an even match.
"We had a good game today but the next match [at home against South Africa in Salta] will be much harder.
"There are things to correct and others that we have to repeat in order to prevent them playing their game."