Star Gallant's victory in the Fountain of Youth Stakes here two weeks ago added to the evidence that he may be the best 3-year-old in America. He could even be this country's best racehorse in years. But one observer was left unimpressed by his four-length victory: Jimmy Croll, the trainer of the second-place finisher, Distinctive Pro.

Croll thought his jockey, Jorge Velasquez, "gave the race away" and subsequently fired him for his transgressions. Croll is probably wrong; his colt is simply not as good as Star Gallant. But his jockey paranoia could nevertheless prove to be a major factor when the 3-year-olds meet again in the $250,000 Florida Derby at Gulfstream Park Saturday.

It could wind up helping the chief rival of both colts, the stretch-running Timely Writer. But no matter how the race develops, the winner is almost certain to emerge as the clear-cut favorite for the Kentucky Derby. Rarely has a Derby prep race seemed so definitive.

Of course, two weeks ago, racetrackers were saying that the Fountain of Youth Stakes would be a definitive test of Star Gallant and Distinctive Pro, two brilliantly fast sprinters who were attempting to go a distance for the first time in their careers. Almost everybody foresaw a gut-wrenching duel between them.

But it didn't materialize. Quite the contrary. Star Gallant took the lead while running the first quarter in a remarkably slow 24 seconds, with Distinctive Pro sitting behind him. Velasquez made a couple of moves thereafter, and twice drew within a length of the leader, but Star Gallant brushed off these challenges and drew away to an easy victory.

Before the race, Croll had been most concerned about getting Distinctive Pro to relax and conserve his energy. Afterward, his hindsight was 20/20. "I told Velasquez not to permit Star Gallant to get an easy lead and to insure a realistic pace," he said. "Velasquez should have made Star Gallant extend himself."

Thus did Croll dismiss one of America's foremost jockeys and hire Craig Perret, whom he extolled as "a good judge of pace." Croll said he doesn't want Perret to go head and head with Star Gallant. But he doesn't want Star Gallant to get an easy lead, either. What Perret is likely to remember is that his predecessor was fired for going too slow early; he won't commit that offense.

The situation may remind some racing fans of the 1976 Preakness. Bold Forbes had defeated favored Honest Pleasure in the Kentucky Derby by taking the lead and setting a liesurely pace. Coming into the Preakness, Honest Pleasure's trainer, Leroy Jolley, was talking a lot like Croll is now. The result: the two horses ran each other into the ground and the long-shot stretch-runner, Elocutionist, beat them both.

The speed duel at Gulfstream may not be so extreme, but there will surely be a realistic enough pace to provide a tough test of Star Gallant, and possibly to give a little edge to the stretch-running Timely Writer. Still, it is difficult to assess the relative merits of the two colts before they meet on Saturday.

Anyone who saw Timely Writer win the Flamingo Stakes at Hialeah had to be impressed by his effort. Breaking from the No. 16 post position, he was parked wide on the first turn, made a strong wide move on the final turn, seized command and was never threatened in the stretch. He has the stamina and the sudden acceleration necessary to win the Kentucky Derby, and the oddsmakers in Las Vegas have properly established him as the favorite in future-book wagering.

There are other formidable stretch-runners in the Florida Derby lineup. Laser Light showed considerable promise as a 2-year-old and has raced only once this season. Royal Roberto looked impressive when he won the Everglades Stakes at Hialeah but the big, long-striding animal never got untracked in the 16-course Flamingo Field.

As good as his competition is, Star Gallant has the potential to dominate all his rivals. He has never been beaten; he has never been seriously challenged; he has never done anything wrong. But Croll's reservations about him still have some validity. Because he was able to get such an early lead in his lone start around two turns, Star Gallant has not demonstrated yet that he is a bona fide distance runner. Saturday, he will have the chance to answer all of the remaining questions about him.