Just as mothers believe there are no bad boys, trainers think there are no truly bad horses. Even if a man happened to find himself training the worst thoroughbred in the world, he would probably manage to detect some virtue, some untapped reservoir of talent in the animal.

It has been possible to test this thesis this winter, because the worst horse in the world has been racing in Florida. He name is Sunshine Mary, and she has compiled a record of futility with few parallels in the history of the sport.

In the first nine starts of her career, Sunshine Mary had never beaten another horse. In fact, she had rarely even been close to another horse, since she would usually break last and drop back.

The Racing Form often had difficulty calculating the distance by which she was beaten because the standard unit of measure -- the length -- is too small. Sunshine Mary lost those first nine races by an average of a sixteenth of a mile. When she made her 10th start in a maiden claiming race at Hialeah last week, she was getting her last chance to achieve respectability.

After he had saddled Sunshine Mary for that event, trainer Louis Underwood said: "I've never had a filly like this in my life." No one challenged this claim, even though Underwood broke into the racing game just after World War I and has trained horses since 1928.

Underwood bought the obscurely bred daughter of Sun Helmet and Mary's Little Pet last fall because he saw some merit in that pedigree: "Her daddy holds two track records on the grass."

And he saw some positive qualities in the filly, too: "She as sound as she can be. She's got a good temperament; she's the best post horse I ever saw. She does everything a stakes horse does. She runs good in the morning; she went five furlongs in 1:06 one day. But she won't run in the afternoon.

When Sunshine Mary lost her racing debut by 25 lengths, Underwood started experimenting. He equipped her with blinkers. He tried different types of bits. He used various jockeys, even trying the bold stroke of letting the worst jockey in Florida, Samuel Mangual, ride the worst horse in American, hoping to achieve some magical chemistry. In their first collaboration, they lost by 49 lengths.

When Underwood ran Sunshine Mary here last Wednesday, he was still hoping to see some improvement -- as were the Hialeah stewards, who had decided to bar the filly if she didn't do better.

In this moment of truth, Sunshine Mary ran the race of her life. She broke 11th in a field of 12, and all the way down the backstretch, she battled with two other cheap maidens in the rear of the pack. Although they were trailing the rest of the field by a considerable margin, they were staging their own race within a race, and Sunshine Mary was fighting gamely. On the turn, she inched ahead of the other two, but the effort proved too much for her. She finally faded in the stretch and finished in her customary position, seven lengths behind the next-to-last horse.

"Well, I can't run for her," Underwood said. "Fillies can be like this."

But he expressed the hope that Sunshine Mary would finally run decently when she got a chance to run on the grass.

Hialeah officials, however, declined to see a future for Sunshine Mary. State Steward Walter Blum instructed the racing secretary's office not to accept any further entries of the filly, marking one of the few times a thoroughbred has been barred from the sport on the grounds of sheer incompetence. Only Underwood would still dispute the justice of the verdict. i