Predictably, the Kentucky gentry are not paying much attention to Maryland's entrant in the Blue Grass Stakes. And, in truth, it is easy to overlook a colt who has never won a major stake, whose trainer is little known, whose breeding is obscure, whose very name is an embarrassment--Deputed Testamony.

But on Thursday at Keeneland, Deputed Testamony can prove that he belongs in the company of the country's best 3-year-olds when he faces Marfa, Copelan, Highland Park and other highly regarded rivals in this important prep for the Kentucky Derby. He may force the skeptical locals to start paying attention to him, and if they do they will realize that no horse has been prepared for the Derby with any more foresight or skill.

For although Billy Boniface is a stranger to the upper echelon of the sport, he has spent most of his life getting ready for this challenge. The son of the Baltimore Sun's now-retired racing columnist, Bill Boniface, he was born with racing in his blood. He started working around the Maryland tracks when he was 14, hoping to be a jockey, ignoring the harsh fact that there aren't many 5-foot-11 members of the riding profession. ("I weighed 107 pounds," he said. "People thought I was going to unveil a coffin when I took my clothes off.")

Boniface worked as an exercise rider for Calumet Farm in 1957 and 1958, when its horses Iron Liege and Tim Tam won the Derby. Then he launched a career as a jockey at Charles Town that proved to be as short as it was undistinguished. Finally, he quit in such disgust that he joined the Marine Corps. "'I just wanted to get the hell away," he said.

While he was stationed in Europe, Boniface had a vision of what he wanted to do with his future. He spent a few weeks of his leave time working on a thoroughbred farm in England, where horses did all their training and were shipped to the track only for races. "I came back home," Boniface said, "with the idea of racing off the farm, European-style."

In 1964, he and his father bought Bonita Farm in Bel Air, Md. They launched what would become a successful breeding operation, and eventually the son was able to do that European-style training. "The advantage," he said, "is that we're able to work all day on our horses, from 7 to 4, and the horses do better in that environment."

Boniface has trained a number of good runners--Berkeley Prince, Lordly Love, Have You--who have achieved success in stakes in Maryland and neighboring states. But Deputed Testamony is the colt who could put him in the big time.

The colt is owned by Francis Sears, an executive for a Boston brokerage firm, who bred his mare Proof Requested to the Bonita Farm stallion, Traffic Cop, for a $1,000 stud fee. Boniface thought a legal-sounding name would be appropriate for the resultant foal, and he asked a lawyer friend for a suggestion. He proposed "Deputed Testimony." Now each blames the other for the misspelling.

But that was the only evident mistake Boniface made with Deputed Testamony. After the colt graduated from claiming races to win the rich Maryland Futurity last fall, Boniface mapped out a schedule that would lead him and his stablemate, Parfaitement, to the Kentucky Derby.

When he worked for Calumet Farm, he had paid close attention to the training methods of Ben and Jimmy Jones, and he said, "One of the things they both had was the ability to point a horse for a particular race. I'm trying to do that, too. I mapped out in January what the horses' races would be and I planned for the Derby to be their fourth start. I wanted them to come into the race fresh."

Parfaitement won his first two starts of the year and finished second in the Wood Memorial Stakes at Aqueduct Saturday. Deputed Testamony, who seems to be the more talented of the two, has stayed on schedule, too. He finished second in a sprint in his season debut, then rallied to win the Federico Tesio Stakes at Pimlico in impressive fashion. He is reaching peak form, and he appears ready to run the very best race of which he is capable. On Thursday he will reveal whether such a performance is good enough to beat the leading members of his generation.