A couple of years ago, when he was just starting in the horse racing game, Dennis Diaz left his home near Tampa to go on a buying trip in Kentucky. He saw a brood mare he liked, Belle de Jour, and a young colt, coincidentally her foal.

Diaz was enticed by the colt's behavior. He was a particularly small animal, and whenever one of the larger yearlings would come over as if to take a run at him, this small colt would buddy-up to one of the bigger, older horses in the area, use it as a shield, a bodyguard. Diaz saw this maneuver as an indication of the colt's intelligence, and bought him for $12,500 at the same time he bought the mare.

The animals were then shipped to Florida, and, by chance, one of Diaz's close friends was present just as the diminutive colt was being unloaded from the van. "Look at what they sold you," the friend said, howling with laughter. "Will you look at this little runt!"

Later that year, Diaz sought to make a substantial profit on the unraced colt by offering him at the prestigious Ocala, Fla., "Select" training sale. But the petition was rejected by sale officials. "They didn't like his looks," Diaz recalled. "Conformationally, they didn't think he was good enough for a 'select' sale."

Linda Diaz remembered it wasn't long after that that her husband -- frustrated by some bad luck with their horses -- walked past the colt's stall and kicked disgustedly at the iron webbing separating man from beast. "Somebody give me $30,000 for this horse," Dennis Diaz shouted imploringly, "and he's gone."

So much for chump change.

Thirty-thousand doesn't get you the colt's left flank today.

And if Dennis Diaz and his wife and partner, the former Linda Elliott of W.T. Woodson High School in Fairfax, get real lucky right here in the 111th Kentucky Derby Saturday, the asking price on the colt might have so many numbers it will look like one of those new zip codes.

"And remember, we own the other, too," Linda said, tantalized by the prospect of playing a pat hand. "We have the factory that makes these . . . ."

We're talking fairy tale here.

We're talking brass ring bingo.

Dennis Diaz had been in the racing business all of 18 months when it came time to name the colt, "and one thing I'd learned real quick is that you've got to spend a buck to make a buck."

So, Spend A Buck it was.

And when Spend A Buck finally got out on the track, the only thing small about him was the time it took him to go from start to finish. A speedball. No doubt about it.

As a 2-year-old he won five of eight races, and doctors suspect that in two of the losses he ran with a bone chip in his front right knee. After successful arthroscopic surgery, he has come back as a 3-year-old to win two of three races, including two blazing track-record outings at Garden State, the last one just two-fifths of a second off Secretariat's world record for the 1 1/8 miles. If you're looking for consistency, Spend A Buck has never finished out of the money. That $12,500 investment so far has returned $991,709.

If you're looking for speed, Spend A Buck is a bullet. That last performance at Garden State was awesome. None of the horses entered in this Kentucky Derby -- not Chief's Crown, whom Dennis Diaz emphatically affirms should be the favorite, nor Proud Truth, nor Rhoman Rule, nor Tank's Prospect -- has come within two seconds of it. Eternal Prince, a highly respected speedster who figures to challenge Spend A Buck for the early lead, hasn't come within three seconds of it.

Was it a once-in-a-lifetime freak? Or was it a glimpse of future greatness? We know Spend A Buck can jet. But how far does his range extend? None of these horses has raced more than one mile and an eighth. Can Spend A Buck sustain his speed for the mile and one-quarter of the Derby? Will the madding crowd unease him? Spend A Buck always has been able to go loose on the lead. Will Eternal Prince play him bump and run?

"Times aren't everything," Dennis Diaz was saying in the early morning chill. "Just because Spend A Buck runs fast doesn't mean he's going to run fast here. He's running against a different caliber of horse here. When horses go out there and run against each other, and look each other in the eye -- and they quite literally do this running head to head -- then heart and class take over."

Exactly how good is Spend A Buck?

That's why they have horse races.

To find out.

Dennis Diaz says he'll know early in the race. Half-a-mile at the latest. "If he's on the lead and relaxing and striding out, if the jockey (Angel Cordero Jr.) is sitting still, not moving his hands, I'll know the horse is going to run a jam-up race. If Angel is having to fight him, and the horse is throwing his head, I'll know we have a problem."

As soon as Dennis knows, he'll tell Linda.

It's an either/or deal.

Either, "We've got a shot."

Or, "Let's go get a double."

They make a nice, fresh package, these owners and their trainer, Cam Gambolati, who used to be a statistician for the Tampa Bay Buccaneers. None of them has had a Derby horse before; they're all very new to the game. People wait a lifetime for a legitimate Derby horse; they've got one in two years. If you listen closely you can almost hear Dennis Diaz apologize for his sudden good fortune. "I was talking to Will Farish, one of the leading breeders in the world. I told him, 'We don't deserve to have this horse -- you do, you've been in this business 30 years.' Why we come up with him, I don't know. Somebody must have meant for us to have him. It's fate, or sheer luck that we caught lightning in a bottle."

There is, by the way, a 2-year-old full brother to Spend A Buck back on the Diaz farm. He is as yet unnamed. Linda Diaz is thinking of Make A Buck. If things go well in the Derby, though, she could be talked into Meg A Bucks.