It is the call Enda Kenny is dreading.
It's sometime late next month and a triumphant Alex Salmond is on the phone to his Irish counterpart. Would the Taoiseach mind having a word in Brussels on Scotland's behalf?
Experts in the Republic have come up with several scenarios, good and bad, that could stem from Scottish independence. Some are already imagining a complete and healthy reappraisal of their fraught but intimate relationship with the island of Great Britain after a Yes vote. Others fear a Yes to independence followed by an English withdrawal from the EU, thrusting Northern Ireland in to no-man's land.
But, writing in the Irish Independent, veteran correspondent John Downing focuses on the simplest diplomatic headache that might come next month: some kind of Scottish appeal to Celtic solidarity as an independent Scotland tries to fast-track its way back in to the EU.
"In Brussels, and across many other member-state capitals, a 'Yes' to independence poses huge challenges and has already led to tensions at many levels.
"Kenny could be also posed with a serious dilemma at EU level. He may be publicly asked to back our Celtic cousins in a row over future membership - bringing separatist and Celtic issues in these islands to the top of the political agenda for the first time since 1922."
Downing cites blunders on all sides of the indyref debate on the EU - including European Commission president Jose Barroso's intervention earlier this year when he said it would be "extremely difficult if not impossible" to get back in to the club. "Many observers," he added, "speculate that London might make a virtue out of the necessity of a 'Yes' vote and extend all neighbourly courtesy and support to counterparts in Edinburgh.
"For many in Brussels, the real enemy of an independent Scotland in the EU could be Spain first and foremost, and then other states such as Belgium, France, Italy and others who face sporadic regional problems with secessionist undertones."
So what happens if a Spain or a France decides to make some kind of test case out of EU membership? "Would Kenny emulate all his predecessors since the foundation of this State and shun all those voicing hopes of Scottish independence?" asks Downing. "Or, would he signal a significant sea change in attitude?"
Spain or France or Belgium aren't necessarily expected to actually go ahead with a veto - although former Irish minister Ruari Quinn asserted earlier this week month that they would.
But such potentially hostile European nations only need to mutter something about even thinking about a block to drag Ireland in to a diplomatic to-do.
And that, reckons Downing, means Ireland won't be wishing Salmond well as September looms. "For this," the correspondent said, "and other reasons, the Dublin Government will have fingers and toes crossed for a 'No'"