Horses sent off at odds of 100 to 1 don't win the Kentucky Derby.

Deonerail came the closest. He was 91 to 1 in the 1913 Derby and forgot his form long enough to defeat the favored Ten Point by a half length. Otherwise, longshots have been long gone here at Churchill Downs the first Saturday in May, running to their odds much more frequently than not.

Yet, this morning, huddled outside Stall 11 in the corner of barn 40 on the Churchill backstretch, were three gentlemen from Caracas, Venezuela, who feel they have a right to dream the impossible dream. They believe it can be done. They know anything is possible in thoroughbred racing.

Luis Navas owns Sir Sir, a Sir Ivor colt capable of being 100 to 1 or more here May 7 in the 103d Derby unless he is coupled with other outisders in the parimutuel field. There can be only 12 betting interests in the race. Sir Sir's improbable price doesn't terrify Navas.

"I once bought a yearling here in Kentucky, in the fall of 1969, for $1,200 who would have been 100 to 1 in the Derby if he had been in the field . . . and he won (in 1971)," Navas recalled.

The colt's name was Canonero, a late arrival from Venezuela. He was 8.70 to 1> bracketed with five other longshots in the field of 20.

Navas is a horse agent, a polite label for a horse trader. He annually buys yearlings and mares in the United States, usually cheaply, to sell back home in Caracas. Canonero was typical. Navas sold him to Edgar Caibett. Canonero ran in Caibett's brown silks on Derby day.

"I made a profit on him," Navas said, "but Mr. Caibett did even better. Much better."

Navas learned from the experience. In July, 1975, when he paid $16,000 for Sir Sir at the Keeneland summer sale, he decided to keep the colt. "This is the only one I've ever owned," he said. "The only one."

Sir Sir was well bred but sold cheaply because of an unsightly right hind ankle that had been stepped upon by his dam. Navas subsequently tried to sell Sir Sir at Hialeah as a 2-year-old but bid him back for $24,000.

Now Sir Sir has a promising future even though the Derby doesn't figure to make Navas rich. A field of 15 to 18 is gathering - some cynics might say "accumulating" - for this renewal of America's most famous cavalary charge.

Seattle Slew is unbeaten, untested and underdeveloped through six starts and will be 1 to 2 or shorter on the Derby tote boards, but that will not deter other owners and trainers from sending their favorite steeds postward. Derby fields are becoming bigger, not better; so much so that the Churchill management has invoked a rule limiting the field to 20, based on earnings.

Sir Sir has collected less than $40,000 through seven races while having more than his share of physical problems.

"Look in there at him, at his back right leg," trainer Leo Azpurua, "that cut was three inches long. Everything goes wrong with him in behind, it seems. He got the cut leaving the gate in his last race in Florida.

"Everything was going beautifully for this horse until his last three races. He had won a stake in Florida! Then he couldn't run for nearly two months. He was coughing. Then he was just beaten by Ruthie's Native and For The Moment in a division of the Florida Derby. He had no chance in the Flamingo. Another horse grabbed one of his legs, at the three-eights pole, and he had to check. Then he got hurt in last race.

Excuses. Excuses. Excuses.

"I know," Azpurua said. "But this horse has ability. I brought Jesus Robriguez up from Caracas to ride him (chades of Juan Arias and Gustavo Avila with Canonero), and we're all set. We're going straight to the Derby. Sir Sir won't run Saturday in the Stepping Stone. Instead, I'll breeze him a mile or a mile and an eighth aaturday or Sunday morning."

Azpurua, Rodriguez and Navas give the Derby its first real international appeal since Canonero, although, unlike Canonero, Sir Sir has never competed out of the country. The trainer is based in Miami but is familiar with the Maryland racing circuit.

"I spent 2 1/2 years studying economics at George Washington," he said. "I loved the city of Washington, back there in 1953 and 1954. It was beautiful, quiet, a nice place to live and study. I remember 1830 Connecticut Ave., the boarding house run by a Polish lady. There were students from all around the world. I enjoyed everthing. Then my father died and I went home without finishing."

Azpurua's family had been in the thoroughbred racing and breeding business for decades.

"My mother always wanted her sons to graduate from college," the trainer noted."My older brother quit school at 19 to become a trainer. I didn't finsih, either. And my younger brother, Eduarodo, didn't quite get through the University of Miami . . . but hte is the top trainer today in venezuela at la Rinconads."

Azpurua is not predicitng a Derby victory for Sir Sir. "All I'll say is that, after Swattle Slew, they all take turns beating each other," he contended.

So second place is not out of the question and , who knows, if Slew gets into trouble because of the large field, perhaps Sir Sir could return a box-car payoff bigger than Donerail did - unless he winds up in the betting grab bag called he mutuel field.

Just remember, while Canonero won the 1971 Derby from way out in left field, the five other horses in that betting conglomerate finished 16th, 17th, 18th, 19th and 20th in the field of 20.