The champion's only loss came after a terrible start

Man o' War had won 20 of his first 21 races. The one that got away began with a bad start, a makeshift barrier, and a colt named Upset.

On August 13, 1919, at Saratoga Race Course, Upset beat Man o' War in the Sanford Memorial Stakes by about a neck. It remains the only defeat in Man o' War's 21-race career. 12

Man o' War arrived at the Sanford as the obvious horse to beat. He had already won his first four starts of 1919, and two weeks earlier he had beaten Upset by two lengths in the United States Hotel Stakes at the same track. In the betting, Man o' War was the odds-on favorite; Upset was only the third choice. 1

But American racing in 1919 did not use starting gates. Horses circled behind a strip of webbing called a barrier, which was lifted when the starter judged the field ready. At Saratoga, several colts broke through the barrier repeatedly, delaying the start. When the field was finally released, Man o' War was in a terrible position: most accounts say he was still circling with his back to the line, while some describe him as turned partly sideways. 1

That left him well behind. Once the race began, jockey Johnny Loftus tried to move up but found Man o' War boxed in by other horses. Tiring rivals checked his progress, and the favorite also gave Upset a 15-pound weight advantage: Man o' War carried 130 pounds, while Upset carried 115. 1

Still, Man o' War nearly erased the damage. Upset held on, with the published result generally described as a win by about a neck; some accounts give the margin as a half-length. The important part is not a disputed inch or two. It is that the horse who had started badly, been trapped in traffic, and conceded weight came within a stride of winning anyway. 1

The result became famous because Man o' War's final record was 20 wins, 1 second-place finish, and 0 thirds in 21 starts. BloodHorse's career summary confirms the same record and identifies the Sanford Stakes as his lone defeat. 2

The next chapter makes the upset stranger, not less impressive. Man o' War met Upset again on August 23 and beat him by a length in the Grand Union Hotel Stakes. The following year, he defeated Upset by a length and a half in the Preakness. Across their careers, Man o' War won four of their five meetings. 1

The horse's name also creates a built-in pun, but it did not create the sports term upset: that word had already been used for an unexpected victory for decades. What August 13 did create was a perfect trivia fact — the greatest horse in the race lost once, at Saratoga, to a rival whose name made the result sound like a definition. 1

That is why the Sanford Stakes still sits in racing history's oddest corner. Upset did not merely beat a champion; he caught an almost unbeatable horse in the one messy, badly timed race that gave the champion no clean chance to run his usual race. And "almost" was still enough to leave Man o' War with the only blemish on an otherwise nearly perfect résumé.