LOS ANGELES - Californians have always loved their Thoroughbred stars, but no horse in many years has excited them as Zenyatta has. They will roar for her at Hollywood Park on Saturday, when she makes her final appearance in her home state and tries to win her 19th consecutive race. Zenyatta inspires fierce passions. When she defeated males in the Breeders' Cup Classic last fall, her fans hailed the performance as one of the best in the history of the event - and maybe in the history of the sport. When the mare subsequently lost the horse of the year title to Rachel Alexandra, her partisans reacted with white-hot anger. The blogosphere is regularly filled with sharp rebukes for anybody who demeans Zenyatta or even suggests that she is not one of the greatest racehorses of all time. Compiling an 18-for-18 career record is an extraordinary feat. Horse races contain so many potential pitfalls that no high-class U. S. horse has put together such a streak since Hindoo in 1881. Nevertheless (at the risk of inflaming the blogosphere), I could not put Zenyatta on a list of all-time great racehorses. My judgment is based partly on the fact that she has compiled her record by running mostly against moderate female competition - such as the field in Lady's Secret Stakes on Saturday. But the main reason for questioning Zenyatta's place in history is that fact that she is a synthetic-track specialist, albeit the best in the brief history of these surfaces. In my view, it is a dubious distinction to be the poster girl for the surfaces that have robbed the sport here of its unique character. California once had the most exciting and vibrant racing in the nation, and East vs. West rivalries animated the sport for decades. While California never had the quality of bloodstock that populated the New York tracks, it had something else: speed. The dirt racing strips in the West were fast and speed-favoring, and trainers accordingly honed horses' speed by training them hard and fast. Jockeys rode aggressive from the gate, and the early pace of races was quicker than in any other racing jurisdiction on the planet. The nature of the game was breathtaking, and fans loved it. When horses toughened by this style of racing came East, they often ran away from their supposedly classier rivals. Fast horses such as Precisionist, Winning Colors, Sunday Silence, Bayakoa, Criminal Type, Silver Charm, and Congaree advertised the virtues of California racing. When California's racing regulators mandated that traditional dirt tracks be replaced by synthetic surfaces as of 2008, they didn't anticipate the consequence of their decision, but they essentially legislated speed out of the game. On the new synthetic surfaces, raw speed was not an asset and sometimes was a significant liability. Jockeys adjusted accordingly. Horses would typically travel at a moderate pace until their acceleration in the stretch decided the race. In the 16 Breeders' Cups races run over Santa Anita's synthetic surface in 2008 and 2009, not a single front-runner wound up in the winner's circle, and most races were won by a horse rallying from far behind. Zenyatta's ability to unleash an exceptional late burst of speed makes her so potent on synthetic tracks. In the stretch run of the Breeders' Cup Classic, she flew past some rivals who had distinguished themselves as powerful finishers. But just twice has she ventured outside of California to run on dirt, beating a good field of fillies at Oaklawn Park in 2008 and a weak group there this year. There is still no evidence that she is as potent on dirt as she is on synthetics. Probably she isn't; dirt and synthetics are so different that few horses are top-class on both. (The 0-for-43 record of horses making the transition from dirt to synthetics in the Santa Anita Breeders Cups laid to rest the cliché that "a good horse can run on anything." Most racing fans regret that owner Jerry Moss and trainer John Shirreffs have been so conservative in their management of Zenyatta that they didn't give her more opportunities to prove herself on dirt. (If the mare had gone East to confront a below-her-prime Rachel Alexandra this summer, she might have won the Zenyatta vs. Rachel debate once and for all.) After Zenyatta's final Hollywood appearance, however, Moss and Shirreffs plan to run her against the nation's best males over the dirt at Churchill Downs Nov. 6. This Breeders' Cup Classic will be the defining race of her life, and if she wins (or even loses a close one), she can silence all of the skeptics. I doubt that she will. If Zenyatta retires without beating top-class competition on dirt, how will history view her? A few years from now, the distinction of excelling on synthetic tracks may not mean much. Amid growing disillusionment with synthetics, Santa Anita this fall is replacing its track with dirt. Hollywood Park will eventually be turned into a real-estate development. At that point there will be only two racetracks in the U.S., both with short meetings, that offer Grade 1 or Grade 2 stakes on synthetic surfaces: Del Mar and Keeneland. When racing fans of the future look back at the record of a mare who excelled on long-forgotten substances called Pro-Ride and Cushion Track, they are apt to regard Zenyatta as a historical curiosity rather than an all-time great racehorse. © 2010, The Washington Post