Wales' hopes of securing a top-four seeding in the 2015 World Cup nosedived after Argentina stunned them at the Millennium Stadium.
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Eleven years to the day following Argentina's only previous victory over Wales in Cardiff, second-half tries from wings Juan Imhoff and Gonzalo Camacho left the reigning RBS 6 Nations champions reeling.
And to make matters worse, Wales also suffered a double injury blow when centre Jamie Roberts and lock Alun-Wyn Jones departed inside the opening 40 minutes.
Full-back Leigh Halfpenny kicked all Wales' points, but they were outplayed by a Pumas team battle-hardened from recent home and away appointments with New Zealand, Australia and South Africa in the southern hemisphere's inaugural Rugby Championship.
Fly-half Nicolas Sanchez weighed in with two drop-goals, two conversions and a penalty, while veteran centre Felipe Contepomi kicked a penalty before he was forced off injured after just 10 minutes.
Wales' interim head coach Rob Howley - in charge while Warren Gatland begins preparations for heading up next summer's British and Irish Lions tour to Australia - will have been dismayed by some of his side's lethargy.
It was Wales' fourth defeat on the bounce, their first at home since last December and a loss that leaves them with little chance of securing a top-four ranking on which top seeds will based prior to the World Cup draw early next month.
They have Samoa, New Zealand and Australia still to come over the next three weeks, with Wales having not beaten the All Blacks since 1953 and suffered seven successive defeats at the Wallabies' hands.
And Wales' day was summed up three minutes from time when substitute back-row forward Rob McCusker burst through - but he blissfully ignored three unmarked team-mates outside him.
It was the final misguided act by Wales, with their players booed off by many in a 51,000-strong crowd.
Wales launched their autumn campaign without injured quartet Jonathan Davies, Adam Jones, Dan Lydiate and Ryan Jones, but Roberts returned after knee surgery in a team that also included debutant prop Aaron Jarvis.
Contepomi and Halfpenny exchanged penalties during a low-key opening under the stadium's closed roof, but there was an impressive tempo to Argentina's game that suggested they meant business.
Sanchez put them 6-3 ahead with a drop-goal after 10 minutes, and there was no immediate sign of Wales getting their much-vaunted wide attacking game into gear.
The Pumas, though, suffered an injury blow when Contepomi was carried off after being left dazed following a midfield collision of bodies. He was replaced by Joaquin Tuculet as Halfpenny landed an equalising penalty.
And the game's fiercely-punishing trend did not end there as Roberts was helped away midway through the half.
It looked as though he had been knocked out following a collision with Pumas centre Gonzalo Tiesi, and it meant an early entry for Perpignan's James Hook, who won his 66th cap.
Halfpenny then completed his penalty hat-trick, putting Wales in front for the first time, but it was largely unconvincing rugby from the home side.
Playing their first Test match since June, Wales looked rusty, although Hook's arrival injected a midfield snap as the home side looked to free wings Alex Cuthbert and George North.
But Wales suffered another injury blow on the stroke of half-time when lock Jones was forced off clutching his ribs, and Wales shaded a disappointing 40 minutes 9-6 in front.
With Contepomi off, Sanchez assumed goalkicking duties, but his opening strike bounced back off the post as Argentina dominated territory early in the second period.
Sanchez then had another opportunity just two minutes later, albeit from longer range, and this time he slipped on making contact with the ball and it fell well short of the target.
Argentina, though, had served notice to Wales they did not intend slipping off the pace, and the home side needed some inspiration, rather than perspiration.
Halfpenny's fourth successful penalty inched Wales further in front, but Sanchez dropped his second goal to make it a three-point game again midway through the third quarter.
Wales could establish nothing in the way of sustained momentum, and the Pumas showed them exactly what do with quality possession when Imhoff sprinted over for a well-worked try that Sanchez converted.
And it got worse for Wales just six minutes later, with Imhoff's fellow wing Camacho the beneficiary this time, finishing superbly in the corner despite Halfpenny's tackle.
Sanchez again converted, leaving Wales in grave danger of defeat unless they could stir during the closing quarter.
But when Sanchez slotted a penalty nine minutes from time there was no way back for Wales, who delivered comfortably their worst performance since folding to defeat against France in Paris 20 months ago.