“This is not a tough horse race,” trainer Rick Dutrow says of the 134th Kentucky Derby, and he is correct in the sense that there is not much formidable competition for his colt Big Brown.

The favorite has won all three of his starts with ease, earning superior speed figures, and none of his rivals has a record remotely comparable.

In an ordinary race, a horse with such credentials might look unbeatable.

But the Derby is no ordinary race, and it is always a tough one, requiring horses to run 1 1/4 miles amidst the chaos of a 20-horse field — something they will never again do in their lives. History indicates that horses must have sufficient seasoning to handle the unique stress of the race.

A horse ought to have raced at least five times in his career to be ready for the Derby. No horse with fewer than five starts has earned a blanket of Derby roses since Exterminator in 1918. Thirty have tried and failed.

Debunkers of the experience factor can argue (correctly) that most of these statistics are based on results from a bygone era. Modern horses race less often than their ancestors, and modern trainers know how to get their horses fit with light regimens. Yet even outstanding horses fail in the Derby if they don’t have sufficient preparation.

Curlin came into last year’s race with an undefeated record in three starts — just like Big Brown; by the end of the year he had proved that he was not only the best colt of his generation but the best horse in the world. Still, he lost the Derby — probably because he didn’t have the seasoning to cope with the rough-and-tumble circumstances he encountered at Churchill Downs.

So even though Big Brown owns the best Beyer Speed Figure in the Derby field, I am throwing him out today. I would not take 2 to 1 on a horse trying to overcome such strong historical precedents. (Nor would I take a short price on a horse breaking from post position No. 20.)

But even eliminating the favorite doesn’t clarify this Derby. The race is filled with unknowns, because of one almost indecipherable factor: synthetic surfaces.

Of the 20 Derby entrants, nine made their last starts on synthetic tracks. Two have never raced on anything but synthetics. What should handicappers make of horses such as Monba and Adriano, who won important stakes on Polytrack after poor performances on dirt? What do we do with Pyro, who ran terribly on Keeneland’s Polytrack after looking like a potential star on dirt? What do we do with Colonel John, regarded as the West’s top 3-year-old, who has never run on anything but the synthetic surfaces in California?

Because of the newness of synthetics, there isn’t much historical evidence to make definitive judgments. But it is clear that racing on dirt and racing on synthetics are distinctly different games, and most horses will prefer one to another. So it is reasonable to disregard any horse who has made his reputation on a synthetic track without showing that he can win a stakes on dirt. Put an X over Monba, Adriano, Cowboy Cal, Bob Black Jack and Colonel John. It may take some courage to eliminate the last one — particularly after his lightning-fast workout over the Churchill Downs surface this week — but he is the probable second choice in the wagering, and I would not take a short price on a horse who has never competed on dirt.

By disregarding the two favorites, a horseplayer should be able to find some lucrative exotic-betting opportunities in the Derby. Yet it is hard for me to muster much enthusiasm or conviction on behalf of the others.

This is a weak crop of 3-year-olds. In a typical year, the eventual Derby winner will come into the race showing that he can run a Beyer Speed Figure in the 105-to-110 range. In this year’s lineup, Big Brown’s 106 is the best, and only six horses have ever earned a triple-digit figure.

Two of these six are Gayego and Z Fortune, who finished 1-2 in the Arkansas Derby. Both earned their numbers honestly; Gayego dueled hard for the early lead; Z Fortune rallied after being parked wide on both turns. For both of them this was a career-best race, and some handicappers will reject a horse who has peaked in his most recent start.

But long-priced horses such as Funny Cide (2003), War Emblem (2002) and Charismatic (1999) all won the Derby after coming to life in their final prep race.

Pyro, by contrast, comes into the Derby after the worst race of his life — his dismal showing on Polytrack. There’s not much history to support the chances of a horse who finished 10th in his final prep race. Yet Pyro is one of only two colts in the field — the other being Big Brown — who have demonstrated exceptional talent. He was dazzling when he rallied from far behind to win his racing debut at Churchill Downs last summer. He earned a Beyer Speed Figure of 105 running second in the Breeders’ Cup Juvenile last fall. His rally to win the Risen Star Stakes at the Fair Grounds in February was so phenomenal that he evoked comparisons to the legendary Silky Sullivan.

This is a colt whose running style always seemed made to order for the Derby, and he had been the favorite in future betting until his Polytrack debacle. Now he is discredited, but he remains the lone horse in the field with both the raw talent and the racing experience that are usually necessary to win the Derby.

My selections: 1. Pyro. 2. Z Fortune. 3. Gayego.