Four horses have run just two prep races. Four others are coming in off long layoffs. And some didn’t even race as 2-year-olds. Conventional wisdom is out the window at this year’s Kentucky Derby, a wide-open affair that could produce a winner whose trainer might just break all the unspoken rules.

Barbaro came into Churchill Downs last year and romped to a 6½-length victory, becoming the first horse since Needles in 1956 to win after more than four weeks off.

“Last year I was the most unorthodox trainer there was and now this year all these people look like geniuses because they’re taking five, six and seven weeks off between the races,” Michael Matz said. “When I did it, it was voodoo.”

Louisiana Derby winner Circular Quay is set to run in next Saturday’s Kentucky Derby off an eight-week break.

“I don’t believe that will be any excuse,” trainer Todd Pletcher said.

Concerned about Circular Quay’s habit of dropping far back, Pletcher believed another hard race too close to the Derby would cause the colt to get lazy in the early going of the 1¼-mile race.

“By being a fresher horse, he’ll lay a little closer to the pace,” he said.

Circular Quay could be joined by such well-rested rivals as Hard Spun (six weeks), Florida Derby winner Scat Daddy (five weeks) and three-week vacationers Curlin and Zanjero.

Pletcher, who also trains Scat Daddy, says many of his horses run better with more time between races. The nation’s leading trainer plans to send out a record-tying five Derby starters in pursuit of his first victory.

“I just don’t see why that wouldn’t apply to the Kentucky Derby,” Pletcher said. “I know you can take all the historical facts and stats and all that, but if I do that, I’m kind of ignoring the most important data and that’s on the ones I train.”

Curlin is 3-for-3 this year, but was unraced as a 2-year-old, which defies long-held beliefs that young horses need all the experience they can get before trying the Derby. His wins include the Arkansas Derby for trainer Steve Asmussen.

“They’re yelling Steve Asmussen’s horse doesn’t have enough experience, but he looks like a pretty nice horse to me,” Matz said.

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Pletcher agreed after seeing Curlin in training on the synthetic track at Keeneland in Lexington, Ky.

“He’s won by lengthy margins and he’s just a very impressive looking horse,” Pletcher said. “He’s sort of bucking some historical trends, but he’s the one horse out there that sort of separated himself from the ones that he’s run against.”

John Shirreffs, who trained 2005 Derby winner Giacomo, brings that horse’s half brother, Tiago, into this year’s race. Tiago ran once as a 2-year-old, which Shirreffs believes was beneficial.

“The more experience they can get at running and being in different situations, the more it’s going to help them later on,” he said. “Going into the Derby in a 20-horse field, there’s a lot of things that happen and you want to have the horse able to handle a lot of situations.”

Circular Quay and Scat Daddy also both ran as 2-year-olds, giving them what Pletcher calls “a tremendous amount of seasoning.”

“They’ve kind of been in a lot of different situations that would maybe prepare a horse mentally for whatever you can throw at them on Derby day,” he said. “Traffic and getting bumped around a little bit and dirt in your face and all those things. That’s an X factor when you go into the Derby with maybe a horse that hasn’t had a lot of that.”