Scotland were “architects of our own demise” in the dramatic 34-31 defeat that gave Argentina a Test series win, says captain Hamish Watson.
The Scots led 28-13 midway through the second half in Santiago del Estero, but the Pumas crossed in injury time through Edinburgh winger Emiliano Boffelli.
Gregor Townsend’s side won their second game last weekend.
“We put them back in the game – when we got there we couldn’t get out of our half,” Watson told Sky Sports.
“Our standard wasn’t good enough today – it’s tough when the lane doesn’t work. We have to stick together and build on that for the fall.”
Head coach Townsend took positive stock of the performance and was proud of his players but accepted that Scotland “should have won”.
“I’m disappointed for the players because it was a chance for a historic win,” he said.
“There were chances to be more specific with our exits in the last five minutes.
“If we hadn’t been stopped over the line it’s different. It’s the players that count and you can see from their reactions how much it means to them.
“I’m proud of the performance away from home. With every game we’ve gotten better on this tour. It would have been a fantastic tour but we didn’t win in the end so the thanks go to Argentina.”
Townsend praised the half-time performances of debutant full-backs Ollie Smith and Blair Kinghorn.
“There was a lot to be proud of,” he said. “This experience is invaluable for our players. Now it’s up to them to drive in preparation to be here in the autumn. We have to be better for these games.”
Scotland again meet Argentina, Australia, Fiji and New Zealand in the autumn internationals.