Thoroughbreds break from the starting game in the first horse race of opening day at Keeneland in Lexington, Ky., on April 4; the track will replace its synthetic surface with dirt before its fall meet. (Garry Jones/Associated Press)

When the Blue Grass Stakes is run at Keeneland on Saturday, it likely won’t produce the next Kentucky Derby winner. Though it was once the most important 3-year-old prep race, it became irrelevant after Keeneland replaced its dirt track with a synthetic surface. None of the seven horses who captured the Blue Grass on Polytrack proceeded to win on Churchill Downs’ dirt; most ran dismally.

The decline of Keeneland’s signature race was only one of the reasons that it announced last week that it will remove the Polytrack and install a dirt surface for its fall meeting. Del Mar made a similar decision last month, and Santa Anita got rid of its synthetic track in 2010. But the decision by Keeneland, a power in the thoroughbred industry, signaled that the movement to synthetic surfaces is finished in the U.S.

The changeover to synthetics was triggered by a series of events in 2006. Barbaro’s fatal breakdown in the Preakness triggered nationwide discussions about horse safety. That summer, Arlington Park and Del Mar experienced epidemics of breakdowns that generated more bad publicity for the sport. Arlington and all of the major California tracks would soon replace their dirt surfaces. Keeneland not only installed Polytrack in the fall of 2006 but became a partner of the company that manufactured it.

The premise that racing surfaces were principally responsible for breakdowns was a simplistic view of a complex problem. Medication policies, trainers’ methods and breeders’ decisions have all contributed to the fragility of contemporary American thoroughbreds, but these factors are hard to fix. The installation of the new surfaces — which were mostly made of rubber, fiber, sand and wax — was a way to demonstrate that the sport was addressing the safety issue.

When regulators and track executives discussed synthetic tracks they focused almost exclusively on safety. They didn’t ask how the new surfaces would affect the sport of racing. Would it be changed? In 2006, most people assumed that synthetic surfaces would resemble dirt, except that they would be safer and easier to maintain.

The various synthetic tracks — Polytrack, Tapeta, Cushion Track, Pro-Ride — fulfilled their promise about horse fatalities. A study by the Jockey Club showed that the catastrophic injury rate on synthetics was significantly lower than on dirt. However, many trainers and veterinarians maintain that horses are more susceptible to hind-end and soft-tissue injuries on synthetics, so the safety argument wasn’t quite as clear-cut as the fatality numbers suggest.

Most synthetic tracks held up well in inclement weather; they were always labeled “fast.” Nevertheless, the promise that they would be easy to maintain proved dead wrong. Seasonal changes and daily temperature changes affect the surfaces significantly, and tracks were plagued with maintenance problems. And they had a relatively short life span. The base of Del Mar’s track was disintegrating after seven summers of use.

But the biggest surprise about the new surfaces was the answer to the question that hadn’t been asked in 2006: What would the racing be like?

Fans quickly observed that it bore little resemblance to dirt. While American breeders have always emphasized speed and handicappers have always understood the importance of early speed, synthetic tracks didn’t favor it. (When Polytrack made its debut at Keeneland, bettors got a quick education when only one of the first 48 races was won by a front-runner.) Horses with good dirt form often didn’t reproduce it on the new surfaces; turf specialists adapted better to synthetic tracks. When the Breeders’ Cup held its championship events on Santa Anita’s Cushion Track in both 2008 and 2009, every race was won by a turf or synthetic-track specialist; dirt runners all failed, including the country’s best horse, Curlin.

The profound difference between synthetic tracks and dirt undermined racing in Kentucky, in the view of many horseplayers. Horses would race on Keeneland’s Polytrack in the spring, but their form would be nearly impossible to assess when they moved onto the dirt at Churchill Downs. The same inscrutability existed when the tracks ran their respective fall meetings. (Synthetic surfaces were more manageable for handicappers at a track such as Woodbine, where horses run on Polytrack from April through December, with few dirt horses shipping in.)

Keeneland’s two short meetings have traditionally been a showcase for the nation’s best thoroughbreds. Stakes such as the Blue Grass, Ashland, Spinster, Alcibiades and Breeders’ Futurity drew top horses from all over the country; the roster of their winners is filled with champions — prior to 2006. Now the country’s good dirt runners rarely show up. Not one serious Kentucky Derby hopeful is in the Blue Grass. The probable favorite, Bobby’s Kitten, is strictly a grass runner, and most of the other entrants are unworthy of a Grades I stakes.

Yet Keeneland is abandoning its synthetic surface with great reluctance — as is Del Mar. Keeneland President Bill Thomason has said he hoped that Polytrack would become so accepted that “everybody would have it.” Del Mar President Joe Harper has been a staunch supporter of synthetic surfaces, but with the rest of southern California now racing on dirt, he acknowledged, “We can’t be the only one.”

In retrospect, the push for synthetic surfaces in 2006 was ill-considered, hasty and a bit arrogant. A small number of the sport’s leaders were saying, in essence, “We are going to change the fundamental nature of horse racing in America,, and we want everyone to fall in line with us.” Upon seeing what the future would look like, too many people — the sport’s customers, especially — wanted no part of it.

For more by Andrew Beyer, visit washingtonpost.com/beyer.