In an undistinguished season for 3-year-olds, Genuine Risk will give Saturday's Kentucky Derby a measure of distinction. She will be the first filly since 1959 to run in the nation's most famous horse race, and she could conceivably become the only member of her sex to win it besides Regret in 1915.

And yet this is a bid for history that trainer LeRoy Jolley evidently didn't want to make. After Genuine Risk's last start, in the Wood Memorial Stakes at Aqueduct, he declared flatly and emphatically that the filly would stay in New York to compete against members of her own sex.

It is the function of trainers to be cautious and prudent; it is in the nature of owners to reach for the stars. Genuine Risk's owners, Bert and Diana Firestone, wanted to run in the Derby, and they prevailed.

Some people wondered if Jolley would quit. Others assumed that the enfant terrible of the training profession would be more sullen and testy than ever at Churchill Downs this week. Instead, Jolley showed up at the track Monday morning and argued persuasively for the merits of this Derby venture.

After Genuine Risk had won all four of her starts as a 2-year-old, Jolley said, "At the start of this season the Derby was somewhat on our mind." But he didn't handle the filly as he handled his male Derby candidate of recent years, such as General Assembly (the runner-up last year) and Foolish Pleasure (the winner in 1975).

They all ran in the usual important prep races leading up to the Derby. Genuine Risk made her first two starts of the season in nondescript allowance races of fillies. Was this a case of equine sexism? Was Jolley denying Genuine Risk the opportunity to mature and develop that colts would get as a matter of course?

Jolley said no. If he had coddled the horse, it was not because she is a filly, but because of the type of filly she is. "You have to judge all horses individually," he said. "Genuine Risk is a large, rangy filly, and I don't think she has the constitution to withstand a whole series of tough races."

After Genuine Risk's two easy victories against Females, Jolley threw her into the Wood Memorial against the well-seasoned Plugged Nickle, early favorite for the Derby. Not surprisingly, she suffered the first defeat of her career. But she did run creditably, finishing third by 1 1/2 lengths.

Still, Jolley had not wavered when he announced his no-Derby decision. What was he doing at Churchill Downs now?

"At the time of the Woods," he explained, "we were looking at a possible 20 horses in the Derby. I had no desire to run in a 20-horse field. Now there are about 12 horses in the race, and that's a world of difference."

Then Jolley and Firestone went to Keeneland to scout their possible Derby opposition in the Blue Grass Stakes. Jolley wasn't worried about the favorite Rockhill Native, but rather with Prince Valiant. "I thought he had the pedigree and the looks of a Derby horse," Jolley said. "I thought he'd run an outstanding race."

Jolley proved to be a less able handicapper than he is a trainer. Prince Valiant finished last by 30 lengths.

"That opened the door," he said. "But still the main thing was the filly herself. If she hadn't been all right we wouldn't have come."

Sometimes a tough race like the Wood can serve as a perfect conditioner; sometimes it can take too much out of a horse. "She's been doing so good since that race," Jolley said, "that I think the Wood will benefit her rather than the other way around. She hadn't run a distance since November; she might have a little more room for improvement than Plugged Nickle."

That argument sounds persuasive. But the history of the Derby suggests that a horse needs more than one good prep race to win here. He (or she) needs extensive conditioning to win a 1 1/4 miles -- the sort of conditioning that Plugged Nickle and Rockhill Native have had, and Genuine Risk hasn't.

With her relative lack of seasoning, Genuine Risk will be at a serious disadvantage on Saturday. She could pull an upset, but more likely she will have to settle for becoming a footnote in Kentucky Derby history.