Former Reds and Brumbies coach Eddie Jones says that when Super Rugby expands in 2016 into Asia only Japan should be considered.
Super Rugby organizers SANZAR confirmed earlier this week that the 18th Super Rugby team will come from eith Japan or Singapore.
Jones who now coaches Japan says that Super Rugby will lose credibility if Japan's bid loses to Singapore.
"In terms of growing the game you'd think they would choose Japan," the former Australia coach told AFP.
"Singapore has no rugby history at all. They would just be coming and plonking a team of Pacific islanders there.
"It can't be the right choice," he added. "That's just crazy."
Jones has coach Japan's "Brave Blossoms" to a record 10 successive wins including last month's 26-23 victory over Six Nations side Italy in Tokyo which has moved them into the IRB's top ten.
"Japan's 10th in the world, has the world's fourth biggest rugby playing population, the world's third biggest economy," said Jones.
"Japan hosts the World Cup in 2019."
"But professional rugby is all about money so there could be other economic factors."
SANZAR have said that they will make the final decision in September or October on who joins South Africa's Southern Kings and a team based in Argentina as Super Rugby's three new teams.
Singapore's bid is believed to be strong as the Asian team will play in the South African group so travel time will be cut by almost half. It is also understood that there is strong financial backing behind the bid.
"Just because it's 11 hours from South Africa?" he questioned.
"You have to take rugby to growth centres, not artificial places."
Sharks coach Jake White who has worked closely with Jones often in his career has called for the new conference fomat to be scrapped and the old strength vs strength format be used again.