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The Belmont Stakes has been staged at three different distances from 1 ¼ to 1 5/8 miles since 1867, when the filly Ruthless won the inaugural by a head.

In 1874, the race was reduced to the current 1 ½ miles and Saxon triumphed by a neck. In 1890-92 and 1895, the final leg of the Triple Crown was cut to 1 ¼ miles, the only times it was the same distance as the Kentucky Derby.

From 1896 through 1925, it was boosted to the original 1 5/8 miles, when American Flag scored by eight lengths. Since '26, when Crusader won by a length, the Belmont has been 1 ½ miles.

For 3-year-olds, the distance is the longest they'll run along the Triple Crown trail or further in their career unless they take to the turf.

That's probably why we haven't celebrated a Triple Crown winner since '78 when Affirmed triumphed over a stubborn Alydar in all three legs. Experts cite various reasons contributing to the drought that ranges from breeding for speed instead of stamina to overuse of medications.

Racing guru Andy Beyer summed it up in a recent Washington Post column:

"The facts are irrefutable. In 1960, the average U.S. racehorse made 11.3 starts per year. The number has fallen almost every year, and now the average U.S. thoroughbred races a mere 6.3 times per year. Almost every trainer whose career spans the decades will acknowledge that thoroughbreds aren't as robust as they used to be.

"There are at least two good explanations for this phenomenon. In earlier eras, most people bred horses in order to race them, and they had a stake in the animal's soundness.

"By contrast, modern commercial breeders produce horses in order to sell them, and if those horses are unsound, they become somebody else's problem. Because buyers want horses with speed, breeders have filled the thoroughbred species with the genes of fast but unsound horses.

"As this change in the breeding world took place, the sport was allowing the use of pain-killers and other medications that are forbidden in most other countries. They allow infirm horses to achieve success, go to stud and pass on their infirmities to the next generation."

For likely odds-on favorite Big Brown in the 140th Belmont, trainer Rock Dutrow Jr. told The Louisville Courier-Journal he didn't think the distance would spell trouble for the colt.

"I'm not afraid of the distance the way he relaxes in his races," Dutrow said. "The way he shuts down in his races, it seems the mile and half is not going to be a problem."

Bob Baffert, who saddled three Kentucky-Preakness winners from '97 to '02 only to see all three Triple Crown bids fail, told ESPN.com he's never seen anything like Big Brown since he has been a trainer.

"Everyone's been waiting for the next Secretariat-type horse, and we got him," Baffert said. "He's going to do it."

Secretariat's Belmont triumph 35 years ago is often called the greatest performance by a thoroughbred. His 2:24 remains the fastest 1 ½ miles recorded on dirt. In addition, the winning margin of 31 lengths is unequaled in Grade 1 U.S. stakes.

The '73 Triple Crown champ achieved something clockers believed never would occur - "negative fractions." That means the 3-year-old ran each quarter-mile faster than the previous one.

Secretariat's mile in the Belmont was even quicker than his eight furlongs in the Kentucky Derby.

While Baffert had good horses, he said, "Big Brown is a great horse. If you have really good horses, a lot of things can beat them. He doesn't get tired. His air capacity must be enormous."

Breeding aside, the son of Boundary won all five career starts at a mile or longer, averaging more than 7 ¾ lengths per victory.

We'll find out on Saturday if Big Brown becomes the 12th Triple Crown champ.