Wales' World Cup campaign was undermined by a lack of options in the front row, says ex-coach Mike Ruddock.
South Africa beat Wales 23-19 in the quarter-finals thanks to a wheeled scrum that saw Duane Vermeulen put in Fourie du Preez for the winning try.
Ruddock says not picking Adam Jones and Richard Hibbard for the tournament left Wales short of powerful scrummagers.
He said the exit "was based on the fact we didn't get scrum selection right before the tournament".
"We were without some heavyweights like tight-head prop Adam Jones and hooker Richard Hibbard in the front row, and we were really a bit underpowered in the scrum once we had replaced Samson Lee [after 55 minutes].
"I am a big believer in scrum power and that lack of power in that crucial moment enabled the South Africa boys to get an angle on the scrum to open up on the blind side, which meant they could get Fourie du Preez over for that try.
"It comes down to moments like that. If you're not quite on the pace, if you're not quite on the technical aspects of any area, a side like South Africa can take advantage of that.
"I would have picked Adam Jones, even to play 40 minutes, and then had Samson Lee on for the second half. That would have given us a much stronger scrum."
Gloucester's Hibbard has won 38 caps for Wales and three for the British and Irish Lions, while Harlequins tight-head Jones has played 95 Tests for Wales and five for the Lions.
Wales coach Warren Gatland started with a front row of Gethin Jenkins, Scott Baldwin and Lee against the Springboks on Saturday, with Paul James, Ken Owens and Tomas Francis their replacements off the bench.
"There were not that many scrums in the game, but every one of them is absolutely vital. That's what we can take from this World Cup," added Ruddock, who in 2005 led Wales to their first Grand Slam for 28 years.
"We can't be too harsh on the 'reserve' props, if you like, and they will have learned so much for the next World Cup."
But despite the loss at Twickenham against South Africa - who Wales have beaten just twice in 1999 and 2014 - Ruddock praised Gatland's side.
"Before the World Cup started I said you never can write off Wales, and the performance was full of courage, character and commitment," he told BBC Radio 5 Live.
"Gatland has done fantastically well, he's a quality coach and Wales are very lucky to have him and the rest of his management team.
"South African nailed it, we can't complain."
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