ARCADIA, Calif. – Rules were made to be broken, and when it comes to the Kentucky Derby, they have been shattered into tiny shards in recent years. A horse had not won the Derby off a layoff of at least five weeks for more than 50 years, that is until Barbaro did it in 2006, followed two years later by Big Brown. Big Brown took down another supposed rule, becoming the first horse in nine decades to win the Derby with a mere three starts. So much for experience. No winner of the Breeders’ Cup Juvenile had won the Derby since the inception of the Breeders’ Cup in 1984. Then along came Street Sense in 2007. Because of that, there has been zero discussion of that factor when it comes to this year’s Derby favorite, Uncle Mo, who won last year’s BC Juvenile, at Churchill Downs, just like Street Sense. And Dosage? It’s not even part of the serious Derby discussion anymore, not since so many horses with supposedly inferior pedigrees found their way to the winner’s circle with the roses draped on their withers. But there is one big one out there, the Moby-Dick of rules, the one that has stood the test of time. For nearly 130 years, since Apollo in 1882, no horse has won the Derby without racing as a 2-year-old. It will be the last rule to fall, and it’s putting up a hell of a fight. Video and chart: Top 20 Kentucky Derby contenders »   Who's Hot, Who's Not » Since 1944, 55 horses have competed in the Derby without starting at 2. Just six of them have finished in the money. The two who came closest to winning were Strodes Creek, who was second in 1994, and Coaltown, who finished second in 1948, suffering the misfortune of being born the same year as his stablemate, Citation. Even horses as talented as Curlin, a two-time Horse of the Year, could not pull it off. Curlin finished third in the 2007 Derby. Two weeks later, he won the Preakness, and by year’s end, he had his first of consecutive titles as Horse of the Year. “Eventually it’s going to happen,” said Steve Asmussen, who trained Curlin. “It’s going to require a horse with tremendous talent, but even with all that you have to have a trip in the Derby.” Here at Santa Anita on Saturday, two horses who were unraced last year, Albergatti and Runflatout, will try to take a significant step towards the May 7 Kentucky Derby when they compete in the Grade 2, $250,000 San Felipe Stakes. Both are coming off victories against maidens. Asmussen is not a disinterested bystander. He trains Albergatti, who made his debut on Jan. 16. He finished second that day, then won his second start on Feb. 12. Runflatout has raced just once. He was an impressive winner of his debut Jan. 29. Both, though, are bucking quite a bit of history. “To make the Derby with a horse like that, everything has to go perfect,” John Sadler, who trains Runflatout, said Thursday morning at Santa Anita. “You’ve got to have a base. But look at Fusaichi Pegasus. He made his first start in late December. Like everything else, that will be broken.” The major hurdle, Asmussen and Sadler agree, is that it will require a horse to go from an unstarted maiden to a Derby winner in, at best, four months. That’s a lot of development in a short amount of time. And there’s the not insignificant aspect of running 1 1/4 miles, in what is now a seemingly requisite 20-horse field. “It’s asking a lot, especially when you are talking about that distance,” Sadler said. “That’s a distance that horses usually drop back from the rest of their careers.” Both Sadler and Jeff Bloom, the executive vice president of West Coast operations for Runflatout’s ownership group, West Point Thoroughbreds, said they are hoping to push on, but are being realistic about the task at hand. DERBY NEWS ON TWITTER: Follow @DRFDerby for news from the Kentucky Derby trail “It’s certainly a balancing act,” Bloom said. “We’d never take any chances that would compromise his ability to progress long-term.” Runflatout was entered twice at Del Mar last summer, and scratched both times because of illness. At the time, he was trained by Carla Gaines. He was transferred to Sadler soon after the new year, still unraced. “He had a lot of experience. He had done everything building up to running in a race. Everything but race,” Bloom said. “Certain horses develop and mature, some require more race experience. Everything comes so easy to him. He doesn’t really get shaken up.” Of the 20 horses currently on the top 20 of Derby Watch, only one, Machen, was unraced as a 2-year-old. “A couple of things slowed us down,” said Neil Howard, who trains Machen. “He had shins. We had to be judicious. We had no choice.” Howard said he thinks the trend toward smaller and smaller pre-Derby campaigns will help yield a horse who equals Apollo’s feat. But he acknowledged that, all things being equal, “battle tested horses always seem to have a little bit of an edge.” “They get bumped around, sort of know the rules already,” Howard said. “It’s like playing college ball before you go to the pros.”