LOUISVILLE – What a bust! The most eagerly anticipated Kentucky Derby in ages, run on a glorious day over a perfect track before a huge sellout crowd, exploded yesterday into the biggest dud of a classic in almost a hundred years.

The race that was supposed to showcase a new superstar of the turf, a colt with all the potential of another Secretariat, pulled more than 156,000 people through the gates – the second-largest crowd in Derby history – in billowing excitement that they were about to witness history.

What they witnessed was an upset of such staggering proportions they could not believe their own eyes. It was not that the winner Giacomo started at 50-1, the second longest longshot in the Derby’s 131 history. Longshots win every day of the week.

What was so dismaying, so unacceptable to true believers, so totally unfathomable even in a sport noted for its unpredictably was that the winner, Giacomo, had won only one race in his career – a run-of-the mill maiden race at Santa Anita in modest time, way back in October last year.

After that less than scintillating exhibition, he ran up five straight losses, including his last, a dismal fourth in the Santa Anita Derby. You’re looking at a very ordinary horse. Indeed, he would have been one of the first horses eliminated on anyone’s list.

I mean, if you’re going to win the Kentucky Derby, surely you have to show some glimpse of ability or class to compete among the elite.

I laughed when his ecstatic jockey, Mike Smith, jumped off and immediately told the media, “I feel so numb, I can hardly feel anything.”

He should have talked to the horseplayers. They weren’t numb. They were keeling over in shock – and bankrupt to boot.

Giacomo, one race removed from a maiden – the lowest rung on the thoroughbred ladder – took on Bellamy Road, the fastest winner of the Wood Memorial in all its history; Afleet Alex, one of the hardest-hitting, best-performed horses of the year. He took on Bandini, the runaway winner of the Blue Grass; and High Fly, the Florida Derby hero.

Giacomo was not eligible to carry a water bucket for any of those stars. Yet, when they faced yesterday’s mile and a quarter, he destroyed them all.

Why? The only explanation might be that this Derby was run at a suicidal pace. Spanish Chestnut, entered specifically to set a whirlwind pace to help his stablemate Bandini, did his job so well he killed his own stablemate and everyone else except – you guessed it – the plugger Giacomo.

Spanish Chestnut, under jockey Joe Bravo, ran the first two furlongs in 22.1 seconds, a mad pace that would test topflight sprinters. He hurtled through the half-mile in 45.1 seconds, one of the fastest halves in Derby history – madness again.

No one could keep pace. Going Wild tried and wilted. High Fly tried and died. Bellamy Road, wide most of the trip, gritted it out to the top of the stretch, when he poked his head in front. Then he collapsed under the heat.

It was left to the one-run grinders to come running late and run over all the exhausted cavalry. So Giacomo outlasted the 71-1 no-hoper Closing Argument. Of the favored horses, only Afleet Alex showed some fight to get third money, ahead of another longshot, the 29-1 Don’t Get Mad.

Under the freak circumstances, Bellamy Road bombed, continuing his owner George Steinbrenner’s lousy year. Any potential the horse had of becoming the new crowd pleaser perished in the dust of the Downs homestretch. But at least he showed some bravery under fire, which is more than you can say for most of them.

Next to Giacomo’s record-rattling triumph, nothing so shocked the crowd as the – let’s be plain and blunt – the stinking performances of so many horses held in high esteem.

Chief among these was Bandini, the 6-1 third choice, who didn’t lift a foot. He beat only one horse home, and that was none other than top trainer Bobby Frankel’s snail, High Limit.

High Fly, Santa Anita winner Greeley’s Galaxy, Lexington winner Coin Silver, 11-1 Noble Causeway and Sun King, the pet horse in the Nick Zito five-horse squad, all finished in the rear, without once offering even a hint of hope. How could so many good horses run so poorly?

My conclusion: This Derby was not a true bill. Far from being a genuine test of the three-year-old crop, it degenerated into the equine equivalent of a barroom brawl, specifically designed that way by the connections of Spanish Chestnut, so that the last horse standing would be crowned and blanketed with roses.

That’s exactly what happened, except the plans misfired. The last one standing was not Bandini – hell, he was the first horse beaten – but a Californian slowpoke who has never run a fast race in his life. What he did have, however, was some stamina and staying power and that was enough to waltz off with the biggest horse race in America.

To the winner goes the spoils and no one would deny Giacomo his day in the sun. But one thing is for sure: there will be no Triple Crown winner this year.