Argentina overpowered a new-look Wales 33-11 in the second Test at Cardiff on Saturday.
Wales coach Wayne Pivac, who had said he was without 27 players for this match because of injuries and British and Irish Lions commitments in South Africa, made seven changes following last week's 20-20 draw with the Pumas at the Principality Stadium.
But an Argentina team featuring nine of the players who started their impressive win over New Zealand last year proved too strong as they outscored Wales three tries to one on a sunny afternoon.
Wales opened the scoring through a try from Owen Lane but Argentina responded with tries from wing Matias Moroni, scrum-half Tomas Cubelli and flanker Pablo Matera, while fly-half Nicolas Sanchez kicked the Pumas' remaining 18 points.
"It's very disappointing," Wales captain Jonathan Davies told S4C's Clwb Rygbi. "The way we trained this week, we'd hoped for a much better performance."
The centre added: "Our discipline was poor and we put too much pressure on ourselves.
"They (Argentina) are a very good side who have had a lot of good results over the past year."
Pivac had made it clear he saw the Argentina series as a chance to develop Wales' squad depth ahead of the 2023 World Cup in France.
The New Zealander's much changed team were dominated at the scrum -- a traditional strength of Argentina's rugby -- and in the air, with the Pumas deploying a simple but effective ball-carrying game against an error-strewn Wales.
"We're disappointed with the result," said Pivac. "The errors we made were far too many for this level of rugby.
The former Scarlets coach added: "We've learnt a lot, not just in matches but in training too. The players will get a lot of work-ons to take away."
Argentina made two changes, with wing Bautista Delguy and centre Santiago Chocobares starting after last week's red card for full-back Juan Cruz Mallia.
Cardiff wing Lane finished well to open the scoring before Argentina hit back as Moroni surged across for a try converted by Sanchez.
Sanchez punished Welsh indiscipline with a penalty before Cubelli, who would have scored earlier but for a knock-on, crossed for a try that was duly converted.
Jarrod Evans kicked a penalty for Wales but Argentina were well worth their 17-8 lead at half-time.
Evans's second penalty did see the hosts close to within a score but fresh indiscipline gifted Sanchez another penalty before Wales full-back Hallam Amos was yellow carded for taking out opposite number Carreras in the air.
Taine Basham's late tackle on Carreras saw English referee Luke Pearce award Argentina another penalty, with Sanchez adding three points to the Pumas' tally.
Sanchez hit the post with a long-range penalty attempt before the No 10 was back on target again.
The dynamic Matera then crossed for Argentina's third try, with Sanchez's conversion completing the scoring.