In London, however, it was Argentina who looked the sharper and more aggressive, with a second-half performance that killed off Welsh hopes of a win.
Wales led 14-12 at the break with tries from Ifan Evans and Rhys Shellard, both converted by Gareth Davies, but from the second-half kick-off the Pumas turned the screw, taking the lead with a try from Diego Palma and then widening the gap with a rare penalty goal from Joaquin Todeschini for a 20-14 lead.
Then when Nicolas Bruzzone breezed crossed for a try, it was all over for Wales, the final score being 27-14 to Argentina.
The result meant that Wales went into the semi-final of the Plate and a difficult tie with Fiji, who had earlier lost to Australia 29-28 and had something to prove to their fans.
In the event the pacific islanders did just that with a dazzling display of running and supporting skills to score three tries, two by Apisai Naiyabo and one by Seremaia Burotu in the first half for a 15-0 lead at the break.
Fortunately for the game and for their own confidence, Wales were able to break the Fijian defence with clever handling that resulted in a try for Lloyd Williams. But it only stirred the Fijians into scoring mode once more, producing a converted try for Randall Kamea and a 22-5 lead.
As full time approached, Wales found the strength to launch an attack that finished with Williams crossing for his second try and a final scoreline of 22-10.
Overall, Samoa extended their lead over New Zealand in the race for the World Series title although neither reached the Cup Final. That was contested between Australia and South Africa with the Wallabies emerging winners by 19-14.
Wales Sevens squad : Jevon Groves (captain, Cross Keys), Rhys Shellard (Cardiff), Ifan Evans (Llandovery), Craig Hill (Newport), Lee Beach (London Welsh), Lee Rees (Scarlets Academy), Alex Walker (Dragons), Rhys Webb (Ospreys), Rhys Jones (Cornish Pirates), Gareth Davies (Cardiff), Lloyd Williams (Blues), Alex Cuthbert (UWIC)
Emirates Airline London Sevens results day two
Cup quarter-finals Argentina 27 Wales 14, Australia 29 Fiji 28, South Africa 17 England 12, New Zealand 10 Samoa 19
Semi-finals Argentina 14 Australia 26 , South Africa 24 Samoa 12
Final Australia 19 South Africa 14
Plate semi-finals Wales 10 Fiji 22, England 19 New Zealand 22
Final Fiji 24 New Zealand 26
Bowl quarter-finals Italy 0 Portugal 41 , Scotland 21 France 12, Canada 21 Russia 12, Kenya 10 USA 19
Semi finals Portugal 24 Scotland 19, Canada 22 USA 17 (after extra time)
Final Portugal 17 Canada 19
Shield semi-finals France 29 Italy 7, Russia 17 Kenya 21
Final France 21 Kenya 24