After calculating every move of his colt Hostage for months, trainer Mike Freeman today had to make one final decision, execute one last piece of preparation for the Kentucky Derby. When it was done, he thought, he could savor the prospect of being the cofavorite for America's greatest horse race.

Instead, he was left to contemplate his broken dreams and, possibly, to wonder if he were partly responsible for the fractured ankle that abruptly ended Hostage's career this afternoon.

After Hostage had won the Arkansas Derby in impressive fashion on April 10, Freeman knew he would need one more long, solid workout to be ready for Saturday's race. He decided that a seven-furlong work today would be optimal, and had jockey Chris McCarron fly here from California for it. But when overnight rains left the track in sloppy condition, Freeman was plainly worried.

"Hostage is a big, long-striding horse," he said in the morning, "and when he runs in that stuff it's hard on him not to get hold of the track. He cuts the hell out of himself. When he ran on a wet track once in New York he cut himself to ribbons, and if the track is muddy on Saturday, he won't run."

Despite the colt's inability to handle mud, Freeman decided he had to go on with the workout. There probably wouldn't be time to wait for a dry track. So before today's first race Hostage walked onto the sloppy surface of Churchill Downs for what would prove to be the last appearance of his life on a racetrack (he will now be retired).

Freeman stood by the rail on the backstretch and looked on as McCarron jogged the colt on the clubhouse turn, galloped toward the seven-eighths pole and then started to accelerate. Then he watched with shock as the jockey stood up, pulled the reins and quickly dismounted before Hostage had traveled an eighth of a mile.

"I felt him take a couple bad steps and he bobbled," McCarron said, "so I felt I'd better pull him up. I don't know what's wrong."

Freeman hoped that his colt had just bruised his foot, or had somehow been bothered by the new shoes with which he had been equipped today. But the X-rays disclosed otherwise; Hostage had fractured the sesamoid bone in his right front leg and chipped another bone in the same vicinity.

"He just did it all in one step," Freeman said. "It was just one of those things that's a million-to-one shot."

It sometimes seems inconceivable that a thoroughbred who has been bred and trained to run fast and has withstood the stress of racing can do such tremendous damage to himself taking one step in an easy workout. But a horse's half-ton weight is supported by very fragile underpinnings, and if his shock-absorbtion mechanism fails for even a split-second--as Hostage's apparently did when he took one bad step in the mud--the results can be devastating.

People who own and train thoroughbreds live with this fear and share each other's pain when it happens. When a serious illness knocked Timely Writer out of the Derby last week, wrecking trainer Dominick Imprescia's months of preparation, Freeman said, "I had the deepest sympathy for the man. But this is part of the game. And it's no game for a sissy."