In the circus atmosphere that always surrounds the Kentucky Derby, there has never been an attraction in the center ring quite like Cassaleria.

Unlike ordinary horses who spend most of their time in an inconspicuous stall, Cassaleria stands in a large cage in the midst of the Churchill Downs backstretch, surveying all the activity around him with his one eye. Most passers-by can't resist staring back.

Outside the cage, the colt's part owner, Tom Gentry, plays the role of sideshow barker; all he lacks is a straw hat and a cane. The most flamboyant promoter in the Kentucky breeding industry, Gentry will take out full-page ads in the Daily Racing Form when one of his horses wins a minor race, and he could scarcely resist the chance to get involved with a claustrophobic, one-eyed horse with a chance to win the Kentucky Derby.

Gentry has Cassaleria T-shirts, Cassaleria bumper stickers. He may have Cassaleria eye patches later in the week.

This may be a trifle hyperbolic, but the one-eyed horse has seen enough glory to earn $355,670 in his career and establish himself as a fairly legitimate Kentucky Derby contender.

Cassaleria was 1 day old when he damaged his left eye in an accident in his stall.

Two years ago trainer Ron McAnally was looking at yearlings on Brady's farm and, he recalled, "When I first saw Cassaleria, the boy brought him out so I was looking at his good side and I said, 'Why isn't this horse in the sale?' Then he turned him around and I saw why. But I was very impressed with his looks. Brady said if I liked him and I'd train him I could have a half-interest in the colt. I was willing to pick up the bills."

McAnally soon discovered that the missing eye wasn't Cassaleria's only problem. Whenever the colt went into a stall, he seemed to be afflicted by claustrophobia, and he would start walking round and round, in endless circles. McAnally tried all the traditional remedies.

"We put a sheep in the stall to settle the horse down and they became companions, but after a week or so he ran the sheep out of the stall. We tried putting bales of hay in there to alter his course. We tried hanging a basketball from the ceiling." Nothing worked. So finally McAnally put Cassaleria in his outdoor pen--a 12-by-12-foot structure with a red pine base, iron bars and a fiberglass roof--and as soon as the colt moved into it, he settled down.

Cassaleria started racing in California last summer, and never encountered any problems because of his limited vision. When he won a maiden race at Santa Anita by 10 lengths, Brady finally had the chance to turn a profit with his once-unmarketable horse. He and McAnally sold 20 percent shares in the colt to three other men--Gentry among them--and retained 20 percent each for themselves. What better name for the ownership of a one-eyed horse than the 20/20 Stable?

Cassaleria promptly won a stake for his new owners, and continued to race consistently well. In the Santa Anita Derby, however, Cassaleria couldn't beat the best 3-year-olds on the West Coast; he finished five lengths behind Muttering. If he were facing an average Kentucky Derby field on Saturday, he would be overmatched. But this is the worst group of Derby horses in at least a decade, and a horse with moderate ability and good luck could win. In the land of the blind, the one-eyed horse might be king.