Racing fans might be shocked by the decision of owner Dennis Diaz to run Spend A Buck in the Jersey Derby instead of the Preakness, but people in the thoroughbred business are not. Even if Diaz had been inclined to pursue the Triple Crown for reasons of tradition, there wasn't a single rational reason or economic incentive for him to do it.

He said as much in his press conference at Garden State Park yesterday. "We have some lead in our pencil," Diaz said, "and we could figure it out."

After Spend A Buck won the Kentucky Derby, Pimlico General Manager Chick Lang tried to dissuade the owner from taking the easy money in New Jersey on May 27. The $2.6 million Spend A Buck could win in the Jersey Derby was trifling, he argued, compared to the $40 or $50 million the colt could be worth if he swept the Triple Crown.

Diaz surely learned after the Derby what experts on thoroughbred economics told The Washington Post: Lang's arguments and his figures were specious. The intangible value of winning the Preakness wouldn't overshadow Garden State's $2.6 million; it might not be worth much at all.

Here are the economics of owning Spend A Buck. The colt's Kentucky Derby victory had made him worth $8 to $10 million now. His rock-bottom value, even if he flops in future races, probably is $5 to $6 million. (Breeder Will Farish reportedly offered Diaz $4 million for a half-interest, and the owner is seriously considering it.)

This figure is relatively modest because Spend A Buck's pedigree is modest, and that is a big factor in his chances of becoming a successful stallion. "He has anything but an ironclad commercial pedigree," said John Finney, president of the Fasig-Tipton Company, which runs the Saratoga Yearling Sales.

In modern-day racing, people have become accustomed to thinking of purse money as nearly inconsequential compared with horses' value at stud. But the $2.6 million available at Garden State is a significant percentage of Spend A Buck's worth. The money certainly is not inconsequential to Diaz, a former insurance man, who says, "We are not rich people."

If Spend A Buck goes on to greater glory, winning major races and proving he is more than a one-dimensional front-runner, his value could soar to as much as $25 million.

Lang is right that winning the Triple Crown would increase Spend A Buck's value greatly. But in the eyes of breeders who would be buying the stallion shares, the Preakness is almost irrelevant. The Belmont is the Triple Crown race that counts.

"I don't see how the Preakness can help him much," said Bill Oppenheim, editor of Racing Update. "It's so firmly established in everybody's mind as a speed-favoring race that he's not going to get any great credit for winning it."

Finney, an expert in thoroughbred valuation, said, "I think, truthfully, that the commercial impact of running in New Jersey vs. the whole Triple Crown series relates entirely to his performance in the Belmont. As a practical matter, it wouldn't matter if he sat out both the Jersey Derby and the Preakness."

Therefore, the choice for Diaz boiled down to this: Go to Jersey for a race you virtually can't lose and will make your horse the third-leading money winner of all time. Or go to Pimlico, where you'd get "tradition," but you'd be running for $300,000 against a tough field where your horse could lose and be devalued by hundreds of thousands of dollars. The amazing thing is that Diaz needed three days, instead of three minutes, to make up his mind.

Undoubtedly, journalists across the country will be calling Diaz unsportsmanlike for bypassing the Preakness. But people who understand the financial choices involved would be calling him something else if he had sent his horse to Pimlico: crazy.