Wales have been warned they face never winning the Six Nations title again if South Africa are permitted to join rugby's greatest annual tournament.
The stark message is also delivered to the other Celtic nations Ireland and Scotland.
The issue of the Springboks potentially replacing Italy to enhance the Championship raised its head again after the Azzurri slumped to their 36th straight tournament defeat, this time at the hands of Scotland.
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Former Scotland coach Matt Williams was scathing of Italy, saying: "On the evidence of today, it’ll be another 36 games before they win a game in the Six Nations.
“Unless there’s fundamental change, the drumbeat for South Africa to be in this is going to get louder.”
However, working in his role as a pundit for Virgin Sport Media, Williams spelt out his fears for the Celtic trio if the world champion Springboks were to come on board.
He warned it would become a straight shootout every year between South Africa, England and France, with Wales, Ireland and Scotland the also-rans.
"I’m going to say something here. If South Africa come into this, the Celtic countries will face not winning the competition again," said Williams.
“That cannot happen. The Welsh, the Irish, and the Scots cannot enter into a competition that is traditionally theirs, where they say, ‘the chances of you winning this in the future are almost nil.’
“How are Ireland, Scotland, or Wales, going to head down to Pretoria at altitude in the summer and win?”
Six Nations bosses insist there are no plans to replace Italy, but South Africa have told southern hemisphere bosses they are exploring their options about leaving the Rugby Championship.
Previous reports say they are set to join the Six Nations as soon as 2025, when the current Rugby Championship TV deal expires, but Italy have warned that would be catastrophic for the development of their own game.
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Nevertheless, private equity form CVC, who have taken a sizeable stake in the Six Nations, are said to want to grow the tournament and feel the pulling power of South Africa would create huge new commercial opportunities.
South Africa's four provinces have already joined the United Rugby Championship and two of them were locking horns with the Scarlets and Cardiff this weekend.
Williams, who led Scotland between 2003-05 and also coached Leinster and Ulster, made his hard-hitting views known despite the proud record Wales have in the Six Nations.
They consistently led the way with the great team of the 1970s and have bagged four Grand Slams and two other titles over the past 17 years alone.
Ireland have also become a force, overcoming England at Twickenham this weekend and battling it out with France on the final weekend for the championship.
Ireland need to beat Scotland and hope Eddie Jones' men do them a favour against the French in Paris.
But Williams believes moving forward the infrastructure in place at domestic level would hand too much of an advantage to South Africa, England and France.
“The problem with international rugby is that it is the result of long-term athletic development. You can’t develop the group required at the national team – it has to be done before they get to the national team,” he said.
“That’s why the academy systems and club systems are so important."
Wales have never won a game in South Africa in the history of matches between the two nations, which date back to 1906.
Six Nations bosses insist they are not interested in discussions to 'replace any participating union', although the talk is not going away.
Italy put up a more spirited showing against Scotland on Saturday, but still succumbed to a 33-22 defeat.
Wales are expected to comfortably defeat them in Cardiff this coming weekend, which would make it 37 losses on the trot.
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