Wales, captained by Leicester Tigers flanker Tommy Reffell, were beaten 39-15 by Argentina in the World Under-20s Championship in Narbonne on Tuesday.
The lead in the fifth-placed semi-final changed hands throughout the first half but scores either side of the interval shifted emphasis into Argentina’s favour.
After an early Argentina penalty, Wales grabbed the opening try through wing Ryan Conbeer after Reffell had claimed lineout ball on the left.
The conversion from Cai Evans made it 7-6, but the lead was shortlived as the Pumas produced one of the tries of the championship as scrum-half Nogues finished off a break by wing Carreras.
With Argentina then a man down following a yellow card, a crosskick from Evans provided a score for right-wing Corey Baldwin, but a penalty try just seconds before half-time following a five-metre scrum gave the Pumas a 15-12 advantage at the break.
They stretched their lead in the opening 50 seconds of the second period, full-back Carreras dotting down in the corner and Wales could only find a penalty kick from Evans in reply before flanker Molina and finally wing Avellaneda completed the scoring for Argentina.
Defeat puts Wales into the seventh-placed play-off against Italy or Australia in Beziers on Sunday afternoon.
Scotland, with Leicester’s Sam Grahamslaw starting at prop, beat Ireland 45-29 in Perpignan in the ninth-placed semi-final this afternoon.
Despite conceding two early tries, the Scots were ahead after two tries from tighthead prop Finlay Richardson and led 24-17 at half-time following a third score from wing Logan Trotter.
Guy Graham added a fourth score for Scotland early in the second half and the conversion put them 14 points in front.
Grahamslaw’s shift was done when he was replaced after 52 minutes but Scotland maintained their momentum with scores from wing Kyle Rowe and back-rower Devante Onojaife to close out the win despite two more Irish tries.
Scotland will play the winners of the tie between Georgia and Japan in their play-off final on Sunday.