ARCADIA, Calif. - The approach to training horses for the Kentucky Derby continues to evolve. It used to be that a horse had to have his last prep no more than four weeks before the Derby. But last year, Barbaro became the first horse in 50 years to end that streak. It used to be that Derby winners had to train extensively at Churchill Downs before the race, but then Funny Cide and Giacomo shipped in just days prior and won.

There has been no definitive final prep for the Derby, with the last five winners exiting the Florida Derby, Santa Anita Derby, Arkansas Derby, Wood Memorial, and Illinois Derby.

But two Derby rules still apply. Not since Apollo in 1882 has a horse won the Derby without racing at age 2. And — with the exception of Sunny's Halo in 1983 — horses with two or fewer preps at age 3 have not won the Derby since Jet Pilot in 1947.

The list of highly regarded Derby starters who entered the race with just two preps at age 3 and failed include such recent favorites as Bellamy Road (2005) and Point Given (2001). This year, Street Sense, the Breeders' Cup Juvenile winner and Eclipse Award-winning 2-year-old male of 2006, will try to buck that trend. He is scheduled to make his first start of the year on Saturday, in the Grade 3, $300,000 Tampa Bay Derby, one of only two starts he is scheduled to have this year before the Derby.

His trainer, Carl Nafzger, said he believes two starts — the second being the Grade 1, $750,000 Blue Grass Stakes at Keeneland on April 14 — will be sufficient for Street Sense, who raced five times at age 2. Nafzger is taking a different approach than in 1990, when he won the Derby with Unbridled, who had four starts at age 3.

"A lot has to do with development," Nafzger said during a conference call this week. "Unbridled was a big, gangly 2-year-old. He wasn't real racey. He needed to run. He needed breaks to win. He was not as matured. This horse has really matured."

Nafzger said that the experience Street Sense gained at age 2 gives him the luxury of not having to do as much this spring.

"He made every race on the schedule," Nafzger said. "He had experience in the slop. He had experience shipping. He had experience on Polytrack and going two turns."

Nafzger said having two starts won't matter "if we get what we expect out of the Tampa Bay Derby."

"I think two races is enough with the schedule he had last year," Nafzger said. "I think it's plenty. If he can't get there in two preps, he wouldn't get there in three."

To be sure, training methods have changed dramatically over the past 30 years, with horses making fewer starts in general. That applies to the Derby, too. In 1976, for instance, the nine runners in that Derby averaged 11.5 starts each before the Derby. That's a career these days. By 1985, the Derby runners averaged 8.9 starts before the race. In 1994, the 14 runners had competed an average of just 6.64 times. Funny Cide and Smarty Jones had run just six times before their Derby wins. Barbaro had run only five times.

Yet, to a large extent, most trainers still believe that past is prologue, and that if only one horse in the past 60 years has won the Derby with just two starts at 3, that is a statistic worth noting. Todd Pletcher, for instance, made three starts this spring of paramount importance for Any Given Saturday, who is scheduled to meet Street Sense in the Tampa Bay Derby, and Circular Quay. And Barclay Tagg, who trains Nobiz Like Shobiz, is sticking to the same three-prep schedule he used with Funny Cide in 2003.

Slideshow   The Week in Sports Pictures The Giants on top of the football world, getting ready for the London Olympics and more. more photos

"I like three preps," Tagg said. "You have to get three preps in them when they're 3-year-olds. Then you've got five weeks to run in three classic races at long distances. It's not easy."

In addition to Street Sense, other prominent 3-year-olds scheduled to have just two starts this spring include Great Hunter, who won the Robert Lewis in his last start; Stormello, the runner-up in the Fountain of Youth; and Ravel, the Sham Stakes winner.

If those horses fail, it will undoubtedly engender second-guessing. But Bob Baffert, who trained Point Given, said that if given another chance, he'd stick to the same schedule. Baffert said he believes the trip Point Given had in the Derby, rather than having just two preps at age 3, was the reason he lost the Derby.

"If I had it to do all over again, I'd have picked an inside post for him and had him covered up," Baffert said Wednesday morning at Santa Anita. "He had the 2-year-old foundation. Great Hunter had a great 2-year-old foundation. So did Circular Quay and Street Sense. Street Sense is a good horse."