Wales interim head coach Rob Howley admitted his side had been made to look lethargic by a battle-hardened Argentina after the Pumas claimed a stunning 26-12 win at the Millennium Stadium.
Tries for wings Juan Imhoff and Gonzalo Camacho in the second half saw the visitors secure their second win over Wales in Cardiff, 11 years to the day after their first.
Howley said: "I am disappointed, frustrated and annoyed because we know we are a better side than that. We talked about it being an arm wrestle for 50 minutes and we were 12-6 ahead but we looked one-paced."
He added: "When you play Argentina, tempo, pace and intensity are important but there is no doubt their experience and exposure to the Rugby Championship has taken that Argentina side to another level.
"They played the All Blacks, South Africa and Australia over a six-week period and they have certainly learned from that and we were exposed to it today and we very much came second."
Wales' chances were not helped when a clearly concussed Jamie Roberts was helped off after a clash of heads with Gonzalo Tiesi, while lock Alun Wyn Jones was withdrawn with a shoulder problem just before the break.
Howley said: "Jamie has a bump on the head, it's a mild concussion to say the least. Alun Wyn has done his AC (joint) so we will have to wait on the medical opinion for that but it does not look good at this time and it will test our strength in depth and these next three games are very important."
Assistant coach Shaun Edwards pulled no punches in his assessment of the performance, and felt Wales had badly missed the injured trio of centre Jonathan Davies, prop Adam Jones and flanker Dan Lydiate, as well as Roberts after he went off.
He said: "I definitely thought the impact from the Argentina bench was better than ours. We went into the game with certain personnel missing and it showed quite dramatically in the last half hour.
"Both starting centres from the Grand Slam were missing, we had our number six and number three missing and it showed, and we have to get the other players up to pace as quickly as possible. But it was obvious there is a disparity at the moment between our first-choice XV and the players who have got those positions now."