Duncan Weir's 78th-minute penalty snatched a 21-19 victory for Scotland in Cordoba against Argentina to stay unbeaten under Vern Cotter.
Two tries from each side helped propel a slow burning Test match towards a dramatic finish.
Scotland arrived at this contest on the back of hard-fought wins over the USA and Canada, while Argentina had lost their two-Test series against Ireland.
Changing all but four of their starting XV was bound to disrupt Scotland's momentum as Cotter continues to suss out the options available to him since taking over after years at Clermont.
His primary focus has to be on shoring up Scotland's work at the breakdown, where Argentina ran riot and won countless penalties to fuel their attacks.
Al Dickinson showed early promise for Scotland in the scrum and it was the tourists who struck first, Tommy Seymour's touchline sprint leaving Argentina in a scramble before he fed inside for Stuart Hogg to score.
Hogg's troubles this season are no secret but this marked a step back onto the right track, his sixth try for his country putting them ahead despite some controversy over the grounding.
Argentina might have been depleted but they didn't lack for skill or flair. A move starting with Santiago González Iglesias' chip over the top ended with their first try, Javier Ortega Desio crossing in the corner after some fine handling.
New head coach Cotter had stressed the need for Scotland to make the most of their chances when deep in opposition territory, but they let a promising passage come to nothing with Argentina forcing them into holding on just inches from the line.
That unforgiving Pumas defence was beginning to dictate, winning successive breakdown penalties and working their way upfield for Sánchez to land a sweet drop goal to put the hosts ahead.
Handling for both sides carrying into contact was an issue, with a high number of errors disrupting the flow of the first half.
Scotland had to find a way to stop the deluge of penalties against them as Sánchez stretched the Pumas advantage with a long-range strike. Another of those golden Scottish chances, winning turnover ball five metres out, ended with nothing as the loose pass flew into touch. Familiar woes.
A set of 20 phases did eventually yield some more points for Weir, his penalty cutting the gap to a single point.
Sánchez responded sensationally, his monster penalty proving to be one that team-mate Marcelo Bosch would have been proud of as he restored Argentina's four-point advantage. Having only won one of their last 12 matches at home, you could understand the home crowd's excitement.
They erupted when Tuculet crossed in the corner, the full-back too elusive for Blair Cowan and beating Hogg to score. At 19-10, Argentina felt home and dry.
Sánchez's departure after a lengthy time on the floor was a cause for concern however, but they survived an onslaught on their try line as Scotland twice turned down points for the corner and twice came up short.
Weir's decision to then attempt a long-range penalty after Scotland decimated the Pumas scrum therefore was bemusing, but he landed the penalty with ease to leave the score at 19-13 and give his side hope.
Hope turned into points. Seymour had enjoyed good space down the left touchline throughout and running into space he released the replacement Henry Prygos for a try that brought Scotland back within a point - putting the onus on Weir to convert for the lead and possibly the win. He couldn't bring it round.
After looking down and out Scotland now had a dramatic finish on their hands. With their rolling maul proving too difficult to stop by legal means, Weir was handed another chance to seal the win with what proved to be the winning kick.
Securing the restart was vital but Scotland couldn't do so, handing their hosts one last shot at the win. Sánchez, who had already done so much, saw his drop goal fall wide to the left. Scotland march on.
Tries: Desio, Tuculet
Pens: Sánchez 2
Drop Goal: Sánchez
Tries: Hogg, Prygos
Pens: Weir 3
Argentina: 15 Lucas González Amorosino. 14 Santiago Cordero, 13 Matías Orlando, 12 Santiago González Iglesias, 11 Manuel Montero, 10 Nicolás Sánchez, 9 Tomás Cubelli (c), 8 Tomás De la Vega, 7 Javier Ortega Desio, 6 Rodrigo Báez, 5 Matías Alemanno, 4 Manuel Carizza, 3 Matías Díaz, 2 Julián Montoya, 1 Bruno Postiglioni.
Replacements: 16 Santiago Iglesias Valdéz, 17 Lucas Noguera Paz, 18 Nahuel Tetaz Chaparro, 19 Tomás Lavanini, 20 Antonio Ahualli de Chazal, 21 Martín Landajo, 22 Matías Moroni y 23 Joaquín Tuculet.
Scotland: 15 Stuart Hogg, 14 Sean Maitland, 13 Nick De Luca, 12 Peter Horne, 11 Tommy Seymour, 10 Duncan Weir, 9 Grayson Hart, 8 Kieran Low, 7 Blair Cowan, 6 Rob Harley, 5 Grant Gilchrist (c), 4 Jonny Gray, 3 Geoff Cross, 2 Ross Ford, 1 Al Dickinson.
Replacements: 16 Pat MacArthur, 17 Gordon Reid, 18 Jon Welsh, 19 Tim Swinson, 20 Chris Fusaro, 21 Henry Pyrgos, 22 Tom Heathcote, 23 Dougie Fife.
Referee: John Lacey (Ire)
Assistant referees: Pascal Gauzère (Fra), Lourens van der Merwe (SA)
TMO: Deon van Blommenstein (SA)