Monday's joint announcement from Racing 92 and Stade Francais which revealed that they are to join forces was met with plenty of consternation.
It's not surprising given that rivalry brews in geographic proximity and over the span of 125 years since their first clash. As the BBC's Chris Jones put it, a merger between the two rugby clubs from the Paris region would be akin to North London Premier League football derby rivals Arsenal and Tottenham deciding to fuse together into one club. It would be unthinkable.
However, it's not without precedent when you look at the long history of sport in Europe. Indeed many of the continent's most famous football clubs were the results of mergers between smaller entities in their formative years.
AS Roma are one of Serie A's most famous clubs. Yet the Italian club's creation in 1927 owes much to a merger between three previous teams.
Fortitudo-Pro Roma SGS and Roma Football Club came together in 1926 to form one club before Società Sportiva Alba-Audace was merged to form one strong entity for in the Italian capital in a football landscape dominated by the cities of Milan and Turin further north. According to Roma's club history, a man called Italo Fascho spurred the union.
Rangers fans outside Dens Park ahead of the Ladbrokes Premiership match at Dens Park, Dundee. Picture by Jane Barlow PA Archive/PA Images
Genoa-based club Sampdoria's name is a clue to their past. Just after the World War II Sampierdarenese and Andrea Doria fused to form a club that would go on to win Serie A in 1991 and reach a European Cup final the following year.
Newcastle United are also the result of a merger between two rivals clubs that were both based in the city. Newcastle East End absorbed some of the playing staff from the folding Newcastle West End.
French giants Paris Saint Germain may have fallen apart at the seams at the Camp Nou last week but they are the product of a union between Paris FC and Stade Saint Germain in 1970 (a Paris FC which split with PSG two years later does exist but has not had anywhere the success of its more illustrious rival).
While the clubs above are just a small sample of organisations that were formed after mergers, there have been other attempts.
Astonishingly enough, there was once a proposal to merge Manchester City and Manchester United in 1964.
City's vice chairman at the time, Frank Johnson, had the type of idea which would be unthinkable today as the rivalry has hardened considerably. And it never gained any traction leaving the two clubs to continue on their merry ways.
In Scotland, the home grounds of Dundee and Dundee United are the closest in Britain and just a stone's throw apart. Both clubs are over a century old but in 1999 they almost came together according to former Scottish Premier League chief executive Roger Mitchell.
He even suggested that the minute details of a new club that would be called Dundee United City Football Club had been thrashed out before the plan fell apart.