Three months ago, Conquistador Cielo was virtually unknown. Now his reputation is so formidable that only three rivals are daring to challenge him in Sunday's Jim Dandy Stakes. His jockey says the colt is faster than Secretariat. Breeding experts are suggesting that he may alter the history of his species. When he is syndicated for stud duty, he will be the most valuable thoroughbred in history.

Is all this acclaim justified?

Conquistador Cielo is unlike the acknowledged superhorses of the past decade--Spectacular Bid, Affirmed, Seattle Slew, Secretariat--all of whom displayed brilliance early in their 2-year-old seasons and sustained it throughout their careers. C.C.'s races as a juvenile seemed rather undistinguished, although the most astute handicapper I know maintained all along that the colt was the best of his generation. He argued that Conquistador Cielo's shins were hurting him so much last year that for him merely to run adequately in stakes company was a remarkable achievement.

Trainer Woody Stephens was unable to get C.C. reasonably healthy until this spring. Since then, the colt is unbeaten--and often has looked unbeatable. He has won five races in a row, two of them major stakes.

Not many horses in history could have run the race that Conquistador Cielo did in the Metropolitan Handicap, blazing the first six furlongs in 1:09 and then finishing the mile in a track-record 1:33. He is undeniably a great miler, but he has not begun to prove himself in the distance races that traditionally determine champions. While his 15-length triumph in the Belmont Stakes may have established him as a superhorse in the pub- lic's mind, his time was not exceptional and none of the animals behind him ran their best race on the sloppy track.

It is a little hard to compare C.C. with the greats of yore on the basis of two victories, only one of which was at a classic distance and which was a little ambiguous. Even to make such a comparison is unfair to a horse like Affirmed, who was a champion in three different years, who battled with Alydar and Spectacular Bid, who won memorable races at all distances from California to New York.

Racing history is filled with horses who have maintained brilliant form for a relatively brief period of time. Earlier this year I thought two other 3-year-olds, Star Gallant and Linkage, were candidates for greatness, but the rigors of a long campaign exposed their shortcomings and proved me wrong. One of the strengths of American breeding and racing is that we demand that our horses pass a variety of tests and display their excellence over a period of time before we consider them great.

Conquistador Cielo represents not a new level of thoroughbred greatness but a new definition of it, a capitulation to values of Europe, where horses may run but a half dozen times in their career and be retired to stud, highly acclaimed. While he may establish his brilliance unequivocally in the Travers Stake here and in Belmont's fall championship series, Conquistador Cielo hasn't even had to do these things to achieve superstardom and to elicit a $40 million syndication offer for his future stud duties.

The breeding industry is largely responsible for this trend; the competition to acquire top stallions is so intense that breeders are willing to pay big money for horses before they have proved themselves. (Just last year, Proud Appeal was syndicated for $10 million before the Kentucky Derby--and then finished 18th).

And the big money encourages owners to manage their horses conservatively. While racing fans would like to see Conquistador Cielo subjected to the most rigorous tests to prove whether he does indeed merit comparison with the likes of Secretariat, he is apt to be managed very cautiously this fall and subjected to a minimum of chancy situations.

Already, racing people are looking ahead to what Conquistador Cielo might accomplish at stud.

Leon Rasmussen, the Daily Racing Form's pedigree expert, wrote before the Belmont that Conquistador Cielo's bloodlines would prevent him from going 1 1/2 miles, but afterward he wrote, "He may be the most important mutation to appear in the thoroughbred breed since St. Simon (1881) became known as 'the prototype of the modern thoroughbred' . . . Conquistador Cielo may be the most significant sire prospect in the last 100 years."

That's an exciting possibility. But the breeding people and others ought to wait until the colt has run a classic distance more than once, engaged in a tough head-and-head speed duel at a distance, conceded weight to good horses, run on the grass or done any of the things that used to be measurements of greatness before they rush to make their final judgment of Conquistador Cielo.