Almost every major racing state offers its own series of prep races for the Kentucky Derby. Top 3-year-olds can spend the spring running for lucrative purses in New York, New Jersey, California, Kentucky or Arkansas.

Because the best horses may not face each other until the Derby itself, handicappers will have trouble drawing lines of comparison and judging who is better than whom. Last year, for example, Spend a Buck was annihilating a bunch of nondescript rivals at Garden State Park, and never faced another top 3-year-old until he went to Churchill Downs.

The clues to Spend a Buck's superiority were the dazzlingly fast times of his victories at Garden State. I calculate speed figures for some of the tracks that offer 3-year-old prep races, but it is practically impossible for a single handicapper to compile good figures for every major track in the country. Finally, after years of trying, I have found the answer to this logistical problem.

I have assembled a network of four speed handicappers and among us we have figures for tracks across the country. We use the same methodology, and our numbers are interchangeable. When Snow Chief came from California to run in the Florida Derby, we didn't have to guess how he stacked up against the top Florida-based horses; the figure he had earned at Bay Meadows gave him a clear advantage.

In our system of numbers, a great 3-year-old like Spectacular Bid or Affirmed might earn figures in the low 120s. An average Kentucky Derby winner (like Pleasant Colony) would have a figure around 117. In a very weak year, a horse might win the Derby with a figure of 112. The figures for the best 3-year-olds of 1986 suggest either that this is a weak crop or that the leaders of the generation haven't emerged yet. Or both. But on the basis of performances this season at a mile or more, these are the top Kentucky Derby candidates:

RARE BRICK (113). His pedigree suggests he should be nothing more than a sprinter, but Rare Brick proved he could go a mile when he won a stake at Oaklawn Park by 11 lengths March 8. He is the only 3-year-old who has shown signs of genuine brilliance this spring, and he could be the Spend A Buck of 1986. But at this point it seems unlikely he could carry his speed a mile and one quarter.

SNOW CHIEF (109). The millionaire colt is the cofavorite in Las Vegas' future-book betting for the Derby, and justifiably so. He has won his last four races with authority. But Snow Chief has campaigned hard throughout the fall and winter, and I doubt he has much room to improve on the figure of 109 he earned in the Florida Derby. (Moreover, he earned that figure with the aid of a track bias; horses on the rail were winning everything at Gulfstream Park.) Somebody is going to be sharper than Snow Chief on the first Saturday in May.

BADGER LAND (106). Trainer Wayne Lukas passionately wants to win the Kentucky Derby, one of the few prizes to elude him in his spectacular career. He is trying to bring his 3-year-olds along slowly so they will reach their peak on Derby Day; Badger Land is likely to do much better than his second-place finish behind Snow Chief at Gulfstream.

COUNTRY LIGHT (106). His impressive victory in an allowance at Gulfstream may have been a one-shot fluke, but Country Light has the pedigree and the connections to be a classic winner. And he is 100 to 1 in the Kentucky Derby future book.

FOBBY FORBES (103). This lightly raced colt was very impressive when he lost the recent Federico Tesio Stakes at Pimlico by a nose to Broad Brush (also a 103). Fanned four-wide on the first turn, he looked hopelessly beaten in midstretch, then rallied powerfully in the final yards. He hasn't stepped into major stakes company yet, but the figures suggest he will be able to do it successfully.

FERDINAND (101). Trainer Charlie Whittingham never asks much of his 3-year-olds and never even thinks about the Kentucky Derby, so he stunned people in California when he intimated he might have a Derby horse in Ferdinand. The superbly bred son of Nijinsky II has lost two straight decisions to a rival named Variety Road (who has a figure of 102), but his over-the-hill jockey, Bill Shoemaker, moved too soon in both those races. Ferdinand is a colt with a bright future.

Several other well-regarded Derby candidates still have not started in major 3-year-old preps yet -- Pillaster, Meadowlake and the Eclipse-Award winner Tasso. Other little-known horses will come to prominence in the next few weeks. Our speed figures should reveal which ones are bona fide Derby contenders and which are not.