When Mine That Bird won the 2009 Kentucky Derby, he blazed a path so profoundly unexpected that to this day expert handicappers wince at his name. Going into the race, nothing was expected of this 50-to-1 nobody from nowhere. And for most of the race, he was dead last—until jockey Calvin Borel made his move from behind the pack, sneaking up tight against the rail and flying past them all. For filmmaker Jim Wilson, the enduring wow factor of the narrative cried out for the big screen. The major studios didn't agree. "Hollywood wanted nothing to do with it," he...