Both came here chasing history and hinting at greatness. Big Brown was unbeaten and trying to become the first horse in 93 years to win the Kentucky Derby after three lifetime races. Eight Belles, a filly, had ticked off four victories, emboldening her owner to run her against the boys in America's greatest horse race. When Big Brown entered the stretch, seemingly finding a gear seen only on sci-fi rocket ships, the 157,000 here to celebrate thoroughbred racing, had their breath taken away by the big colt's dazzling burst. When Eight Belles broke from the pack to give determined chase, many checked their programs, “Was that really the filly?” Big Brown hit the wire nearly five lengths ahead of Eight Belles, but moments later, there was heartbreak. While Kent Desormeaux was galloping out Big Brown, Eight Belles fell and had to be euthanised soon after passing the winning post. She had fractured both of her front ankles, said the Derby's on-call veterinarian, Dr. Larry Bramlage, and was euthanized on the racetrack. The Florida Derby winner and favorite here became the first horse to win America's greatest race from the 20th post since Clyde Van Dusen in 1929. Two years earlier, Barbaro's breakdown in the Preakness and his death months later helped speed the adoption of synthetic racing surfaces, Eight Belles's death is bound to raise new questions about the safety of traditional dirt tracks like Churchill's and lead to second-guessing over whether a filly, which usually runs against other fillies, should have competed against colts. It was a sorrowful end note to what had been 2 minutes 1.82 seconds of scintillating horse racing, punctuated by the bravura performance of Big Brown. For two weeks, the colt's trainer, Richard Dutrow Jr., had sounded like Muhammad Ali before a big fight as he predicted victory and scoffed at historical precedent. Big Brown moved around the first turn four wide but galloped nicely as he stalked the leaders. He was sixth at the far turn but at the top of the stretch exploded past the field for an easy win. “When he turned for home, I knew the game was over,” said trainer Rick Dutrow, Jr. “We were going crazy. Turning for home, you could see no one was going to catch him.” Denis of Cork finished third of the 20 runners in the mile-and-a-quarter race, 3 1/2 lengths behind Eight Belles. Dutrow said he was unsure when Big Brown would ship to Baltimore's Pimlico Race Course for the May 17 Preakness Stakes, the second leg of thoroughbred racing's Triple Crown series. No horse has won the Derby, Preakness and Belmont Stakes since Affirmed in 1978.