Former Welsh lock Gareth Llewellyn says Wales did not capitalise on the time when New Zealanders Graham Henry and Steve Hansen were in charge.
New Zealanders Graham Henry and Steve Hansen both coached Wales
Henry coached Wales from 1998 to 2002 and Hansen took over until 2004 but Llewellyn says standards had already slipped by the 2005 Six Nations.
"There's been resentment from Welsh coaches and we've failed to learn the lessons that they brought," he said.
"After they left we ended up with a group of frustrated players."
Speaking on BBC Wales' Scrum V on the Radio programme, Llewellyn, currently playing and coaching with Bristol, said the quality of training dipped from the Henry-Hansen era.
That was despite success in 2005 when, under Welshman Mike Ruddock, Wales won their first Grand Slam since 1978.
"We won the Grand Slam deteriorating as a team; it wasn't a great Six Nations, the other teams weren't great and we probably had one great performance against Ireland," said Llewellyn, who won 92 caps for Wales.
"There was not greater respect for a foreign coach because he was foreign, there was greater respect because the things they put the players through on the training field made the team able to produce better rugby."
However, former Wales captain Kingsley Jones, speaking on the same programme, said he wants the next national coach to be selected from home-grown candidates.
The Welsh Rugby Union has cast its net wide in the search for a successor for the sacked Gareth Jenkins.
The likes of South Africa coach Jake White and a clutch of New Zealand's best coaches are all in the frame.
"I'd like to see a Welshman coaching Wales... rather than chasing coaches and making it a Dutch auction," Jones said.
Maybe the timing is not right for David Young or Phil Davies
Sale Sharks coach Kingsley Jones
"New Zealand have got good coaches, of course they have, but I don't see why we need to give those guys experience of coaching international rugby and then they go back and use it to coach New Zealand."
Hansen and former Wasps coach Warren Gatland are both thought to be targets for Wales.
But the WRU is also believed to want to hold informal talks with the coaches of the four Welsh regional domestic teams - Cardiff Blues coach Dai Young, Ospreys coach Lyn Jones, Llanelli Scarlets' Phil Davies and Paul Turner at the Newport Gwent Dragons.
"Maybe the timing is not right for David Young or Phil Davies, I don't know," Sales Sharks coach Jones added.
"But I'd like to see one or two of those guys, maybe together, maybe with (Ospreys assistant coach) Sean Holley taking Wales forward."
Meanwhile, Jones ruled himself out of the running this time around.
"I'd love to move on to that when I'm right and ready for it, it's all about the timing really," Jones added.