In his illustrious racing career the great Man o' War won all of his horse races except one, the Sanford Memorial Stakes, where he lost by a neck. What was the name of the horse that beat him?

History Trivia: In his illustrious racing career the great Man o' War won all of his horse races except one, the Sanford Memorial Stakes,  where he lost by a neck. What was the name of the horse that beat him?