The euphoria of Argentina's opening World Cup qualifying win over Chile vanished at a stroke on Tuesday as the two-time world champions slumped to an historic 1-0 loss to Venezuela.
Fernando Amorebieta bagged the only goal to stun Alejandro Sabella's side and send them back to square one, just when it seemed Friday's 4-1 thrashing of Chile had exorcised demons of a summer Copa America failure on home soil.
After the Chile game, Sabella, who replaced Sergio Batista in the wake of a Copa quarter-final loss to eventual champions Uruguay, had ventured that the team had laid to rest an "apparent collective psychosis" regarding how Lionel Messi fits into the national team.
Last Friday, Barcelona wizard Messi had shone as brightly as ever in the national shirt, scoring one and laying on another for Real Madrid's Gonzalo Higuain.
But that was Buenos Aires.
On Tuesday it was a hot and sticky Puerto La Cruz in the Venezuelan Caribbean, which saw Argentina fail to kick on from last week's promising showing.
Amorebieta's powerful header from a corner on the hour settled the contest at the Jose Antonio Anzoategui, where the visitors huffed and puffed but proved unable to blow the Venezuelans' house down, making Argentina's home date with Bolivia on November 11 a must-win affair.
The hosts had also come into the qualifiers determined to prove themselves and desperate to show that their first ever run to the Copa semi-finals was no fluke, after an opening qualifying loss in Ecuador.
Messi and Higuain sought in vain to impose their experience on the encounter as Venezuela stuck doggedly to their task.
In desperation, Sabella threw on Paris Saint-Germain's budding star Javier Pastore for Angel Di Maria, but to no avail.
Sabella said afterwards that the sticky conditions had been a factor.
"Maybe the heat was a factor, the humidity, the fact we played Friday and then had to travel," he said.
"But we have to take things game by game and look at the things we need to work on -- the qualifiers are a long road."
Sabella aded: "It was a game of two halves. The first, in general, was all Argentina -- we had a few chances. The second was different in that they had more of a midfield presence and started throwing people forward."
Counterpart Cesar Farias was delighted.
"This team asked a lot of the right questions and when you do that, you (can) come up with some fine responses. This is important and gave us an historic victory," said Farias, whose charges next travel to Colombia.
Argentina now trail Uruguay, who conceded a late equaliser in a 1-1 draw against Paraguay, the side they defeated 3-0 in the Copa final.
Veteran Uruguay forward Diego Forlan netted his 32nd goal in the national shirt midway through the second half to move beyond the mark he previously shared with 1920s and 1930s hero Hector Scarone.
But in a dramatic finale, Richard Ortiz snatched the equaliser with seconds of injury time remaining.
"It was intense and there weren't many chances," said Uruguay coach Oscar Tabarez, whose men now top the group by a point and who next host Chile.
But he added that "every point is a step nearer the goal" of qualifying as one of the best four sides in the group, this time shorn of already-qualified 2014 hosts Brazil.
The team finishing fifth can also qualify via the play-offs.
Elsewhere on Tuesday, Colombia edged out Bolivia 2-1 in La Paz courtesy of a late goal from Atletico Madrid's Radamel Falcao, who had only come on 12 minutes earlier in place of Teofilo Gutierrez.
"This was all planned," said Colombia coach Leonel Alvarez. "I talked with Falcao and after Teo (Gutierrez) had put in his shift Falcao, came on fresh as a daisy."
Bolivia generally fare well at 3,600 metres altitude at their Hernando Siles stadium but this time were outfoxed.
In the other game, Chile beat Peru 4-2 in an entertaining encounter, with Waldo Ponce, Eduardo Vargas, Gary Medel and Humberto Suazo on target for Chile, while Claudio Pizarro and Jefferson netted consolations for Peru.