Art Sherman, the 77-year-old trainer from California, is the story of this year’s Kentucky Derby, America’s greatest classic to be run for the 140th time at Churchill Downs on Saturday.

Sherman, once the exercise rider for 1955 Kentucky Derby winner Swaps, is a 60-year racing veteran who gets his first shot at the Derby with the favourite California Chrome.

"All the years you put into this game, this would just be a dream come true to win," Sherman said.

"This horse is my California rock star. I'm just his manager.

“As a 3-year-old he has been getting better and better. He's a different horse right now and he's touting me.

"But at the same time I'm very satisfied with my career. I never made it with the big, big horses, but

“I just look at the young people coming in and I hope they have as good a time as I've had.”

If ever a favourite rolled up to the Kentucky Derby in effortless form it has been California Chrome.

He has galloped to victory by a combined 24.25 lengths in his past four starts, culminating in the G1 Santa Anita Derby by 5.25 last time out. He has since attracted a $6 million offer for a 51 percent share that has been rejected by his working-man owner breeders Steve Coburn and Perry Martin.

But it’s a Kentucky Derby and as always questions linger over the head of the favourite. He’s a forward running speedster, which immediately raises will he handle the quicker pace of the Derby, the 1 1/4-mile distance and cavalry charge into that tricky first turn?

Could he look another rival in the eye for a dogfight to the line?

There are queries on how strong was the competition California Chrome faced on the West Coast compared to Derby runners that have prepped in the East like New York’s Wood Memorial Stakes winner Wicked Strong and runner-up Samraat or those who came through the Arkansas Derby such as winner Danza and runner-up Ride On Curlin.

Others are critical of the way he has trained on the Churchill surface since his arrival in Louisville.

Hall of Fame trainer D Wayne Lukas has summed up the challenge facing California Chrome.

"If you're a numbers person, you're going to have to like that horse," said Lukas, who does not have a runner this year. "But when you throw him in there, even as dominant as he has been in his races, give him 18 other horses to look at with everybody riding a little more aggressive on a strange track going a distance he has never run, it really changes the game."

Danza, one of four runners from Todd Pletcher’s mega stable, has been a trackwork buzz horse, training powerfully at Churchill since his breakthrough victory in the Arkansas Derby.

However Pletcher’s Risen Star Stakes winner Intense Holiday, who was second in the Louisiana Derby in his last start, blazed through the most visually impressive work of Derby week last Sunday, his Derby stocks rising dramatically after he easily separated himself from his workmate, the Spiral Stakes winner We Miss Artie.

"I would classify this as the best work I've seen from him," Pletcher said after Intense Holiday's move. "He always trains well and it's normal for him to breeze well, but that was exceptionally good."

Pletcher, who won the Kentucky Derby with Super Saver in 2010, will also send out Sam F. Davis Stakes winner Vinceremos, who must return to better form following a 14th in the Blue Grass Stakes on the Polytrack at Keeneland.

California shipper Dance With Fate won that race and did so impressively for trainer Peter Eurton, but has always presented better form on synthetic tracks, evidenced by his Breeders' Cup Juvenile run on dirt where he finished eighth.

Medal Count is one who has versatile form over multiple surfaces and seems to be relishing the Churchill track.

Trainer Dale Romans took an unsual path with the son of Dynaformer after he won the April 4 turf Transylvania Stakes at Keeneland, wheeling Medal Count back to the April 12 Blue Grass where he finished a good second to earn his way into the Derby field.

On dirt, Medal Count has only an 11th-place finish in the Breeders' Cup Juvenile and a fifth in the Fountain of Youth, but he has been training powerfully leading up to the Derby.

Romans said he has never backed up a horse so quickly at this level, but "you have to remember, all horses are horses; it doesn't matter what level. He improved from one race to the next.

“I think he's a horse that improves with work. He's doing super; I'm not even stressing about him, he's doing so well."

Three horses enter the Kentucky Derby off the Wood Memorial - Wicked Strong for trainer Jimmy Jerkens; Len Riggio's previously undefeated Samraat who finished 3 1/2 lengths back for trainer Rick Violette; and fifth-placed Uncle Sigh, who races for Anthony Robertson.

Uncle Sigh and Samraat thrilled in the early preps with their furious battles in the G3 Withers Stakes and G3 Gotham Stakes at Aqueduct.

Meanwhile in Florida, Wildcat Red and General a Rod hooked up for battles in the Gulfstream Park Derby, Fountain of Youth and Florida Derby.

Wildcat Red emerged on the winning side in the Fountain of Youth for Venezeulan trainer Jose Garoffalo after taking the Hutcheson Stakes. General a Rod took the Gulfstream Park Derby and was second in the Fountain of Youth, then settled for third in the Florida Derby.

Joel Rosario, last year's Kentucky Derby-winning jockey, gets the mount on General a Rod, who was purchased by Starlight and Skychai Racing from Jose Rodriguez this past week.

Ride On Curlin continuously hits the board and is one of three horses trained by "Bronco" Billy Gowan.

He ran 4 3/4 lengths behind Danza in the Arkansas Derby and was third in both the Rebel and Southwest Stakes and was G1 placed last season in the Champagne Stakes at Belmont.

A bonus is his rider, three-time Kentucky Derby-winning jockey Calvin Borel.

Candy Boy has also been a consistent performer, and comes in off a third-place finish in the Santa Anita Derby for trainer John Sadler.

He won the G2 Robert B. Lewis Stakes with a good three-wide bid late, and will be ridden by Hall of Fame jockey Gary Stevens in pursuit of his fourth Kentucky Derby win.

Tapiture, trained by the embattled Steve Asmussen, had been highly regarded after his easy Southwest Stakes score earlier this season and a previous romp in the G2 Kentucky Jockey Club at Churchill as a 2-year-old.

But his odds climbed after a runner-up finish in the Rebel Stakes and a lackluster fourth in the Arkansas Derby.

Asmussen is under investigation for allegations of animal abuse and improper conduct from the watchdog group People for the Ethical Treatment of Animals.

Hall of Fame trainer Bob Baffert has been left with one starter, G3 Sunland Derby winner Chitu after the late defection of his Rebel winner Hoppertunity due to a foot issue.

Pablo Del Monte also opted not to run, setting the field at 19.