At a time when the proposed Sovereign Series encounters resistance at every turn, much of it from commentators with axes to grind, one initiative that would have truly identified a world champion racehorse predictably faltered in New York on Saturday. Curlin, America's Horse of the Year, succumbed on his turf debut to the Brian Meehan-trained Red Rocks.

That single brushstroke illustrated just how perplexing is the concept of coralling the sport into a format that crowns a “champion racehorse”. Clumsy efforts persist, yet Curlin's defeat re-emphasised that racing in different countries has become so diverse as to be irreconcilable beneath a “champions” banner.

It is said that rugby union derived from William Webb Ellis's desire to handle the football. The two sports have since become so unrecognisable from one another that any attempt to unite them would be laughable. So it is with American dirt racing and its counterpart on turf in Europe. The two codes are poles apart.

Curlin did not remotely resemble himself on Saturday. An entirely new set of circumstances essayed his defeat by Red Rocks, who has yet to win a group one race in Europe. Strengths that have propelled Curlin to exalted heights on dirt were neutralised by the different demands of racing on grass. Here are two for starters.

Curlin's greatest strength is his attritional, grinding style, yet he ran on a surface that favours acceleration. He is also an unlikely horse on pedigree to stay ten furlongs. While dirt racing regularly mocks such theory, it is not true of grass. The son of a miler from a mare of sprinting origins would be expected to weaken towards the end of an 11-furlong grass race, which is exactly how Curlin ran on Saturday.

That he ran on turf at all is to be applauded. He may yet try again in pursuit of a place in the Prix de l'Arc de Triomphe. Should he do so, it will be a challenge born of old-fashioned sporting virtues. No Sovereign-style bonus could lure a horse who has already banked $10 million - and is worth seven times that sum for stallion duties.

The problem for Curlin's connections is that they can only guess at which aspect of Saturday's race usurped their horse. They have detailed knowledge of his requirements on dirt, over which he has assimilated his formidable reputation. If he has climbed many ladders, his turf debut was akin to the long, slippery snake that took him back to the start.

It speaks well of Curlin's crew that they opted for a genuine attempt at a turf campaign - as opposed to European horses that close their careers with a one-off swipe at the Breeders' Cup Classic. They may even cite Curlin's propensity to get beaten on his first run at a new venue as reason to persist.

First-up dirt defeats at Churchill Downs, Belmont Park and Monmouth Park were all avenged with thumping victories on Curlin's return to those tracks. That is why he ran in a meaningless prep at Nad Al Sheba before his rampant Dubai World Cup triumph.

In reality, however, Curlin is tilting at Arc windmills. Two more imponderables - soft ground and right-hand bends around which he has never raced - would confront him in Paris. And let's be honest: who enjoys the sight of a magnificent horse reduced to the common herd by a set of disadvantageous circumstances?

More power to his people, who have demonstrated a sense of adventure way beyond what most others would dare with such a valuable asset. Nevertheless, the desire to unite turf and dirt racing in pursuit of a world champion remains elusive. The concept will only survive in the name of sport, and the guise of Curlin's crew.

The Dubai authorities realise this, which is why World Cup night serves up a mix of turf and dirt races. And there is surely a message here for originators of the Sovereign Series if they believe that the horse accumulating most points is truly the champion. The series makes sense from a marketing perspective, but that is another matter entirely.