Curlin working over the Santa Anita Pro-Ride, October 2008 (Benoit)

Horseplayers unfamiliar with synthetic surfaces faced a conundrum when Breeders’ Cup races were held last fall at Oak Tree. Should dirt form be completely discounted? Did turf horses really deserve extra credit on synthetics? Could the handicapping really be that different?

If the answers weren’t obvious already, they were driven home with an exclamation point when European longshots Raven’s Pass and Henrythenavigator roared past Curlin in the stretch of the Classic.

Yes, synthetic racing is a different animal from dirt racing, just as dirt racing is different from grass racing.

Some horses do well on both surfaces, or in the case of Einstein, on all three. But as the Breeders’ Cup prepares for back-to-back spins in Southern California, contrasts between Eastern dirt form and Western synthetic form cannot be overemphasized. That’s the primary reason Curlin — the best dirt horse in the world in 2008 — didn’t win the Classic, and why Rachel Alexandra won’t be running against Zenyatta this year.

Synthetic racing is actually like a first cousin to turf racing, and a second cousin to dirt.

Horses struggle to get through the loose sand of dirt tracks, and fatigue more rapidly as a result. That’s why most dirt races are run in a state of constant deceleration, and in what would seem to be a contradiction, why frontrunners tend to be more effective. By the time horses reach the stretch on dirt, even stretch-runners are fatigued, and while they can gain ground and sometimes win, often they simply can’t muster enough energy or get enough traction. Thus the dirt phenomenon of speed horses stumbling home to win although they’ve been clearly exhausted for a furlong or longer.

You see that happen much less often on grass, and almost never see horses flying home in 22-and-change on dirt.

On grass and synthetics, horses get more traction and firmer footing. That creates less fatigue. And we’ve repeatedly seen that extra energy and better traction — not to mention more forgiving kickback — give come-from-behinders an advantage through the stretch. It’s why wire-to-wire winners are less common on grass and synthetics and why jockeys employ less-aggressive strategies. It’s why Euros who become excessively fatigued on dirt and frustrated by kickback — and who are trained to finish with a flourish — are much more effective on synthetics.

Of course, synthetic racing is still horse racing, and the best horses can win regardless of surface. But Breeders’ Cup horses are the most accomplished in the world, and fields tend to be more evenly-matched. Such races can be determined by small differences, and the impact of a synthetic surface is anything but small.

Last year, horses with previous synthetic form dominated those that had none. Europeans were no longer throw-outs in main-track races. Those results are in the books. This year, horseplayers should feel no such conundrum.