The 140th Kentucky Derby takes place at Churchill Downs on Saturday and the early favorite has American race fans giddy with excitement.

California Chrome has been installed as the short-priced favorite to win the annual Run for the Roses after demolishing his opposition back in the Golden State.

The three-year-old has romped to victory in each of his past four starts, including the Santa Anita Derby, by a combined margin of more than 24 lengths.

His performances have raised hope this year's race will produce another champion to emulate the likes of Secretariat and Seattle Slew by winning the Triple Crown.

California Chrome's jockey, Victor Espinoza, has already won the Derby before, with War Emblem in 2002, while his 77-year-old conditioner Art Sherman is bidding to become the oldest winning trainer.

"He's feeling good and he's doing good," a confident Sherman said, "He's coming up to this race right."

It has been 36 years since Affirmed, in 1978, became the last horse to complete the Triple Crown so the odds are still heavily stacked against California Chrome.

But bookmakers have been impressed by what they have seen so far from the chestnut, initially listing him at odds of 5-2 after he drew perfectly in barrier five for the 20-horse race.

But he could start even shorter on race day after the second favorite, Hoppertunity, was scratched on Thursday because he had a sore foot and replaced by the first alternate, Pablo Del Monte.

"Unfortunately, the timing is horrible because we don't have enough time to work on the foot," Hoppertunity's trainer Bob Baffert said. "It's tough, this close to the Derby but the horse is fine."

The second pick now is the 6-1 chance Wicked Strong, named in honor of the victims and survivors of last year's BostonMarathon bombing. A surprise winner of the Wood Memorial, he will be ridden by Jamaican-born jockey Rajiv Maragh but drew badly in barrier 19.

"The one positive is that he's not in the gate very long," said trainer Jimmy Jerkens. "I'm trying to convince myself that it's not a bad post, but I don't know if I can."

Danza and Intense Holiday share the third line of betting at 8-1. Both are trained by Todd Pletcher, who won the race in 2010 with Super Saver and has four starters this time.

Danza moved into calculations after winning last month's Arkansas Derby while Intense Holiday earned his trip with a second-place finish in the Louisiana Derby.

Trainer Mike Maker has three runs in the race, including the Louisiana Derby winner Vicar's in Trouble, which will be ridden by Rosie Napravnik, who is bidding to become the first female jockey to win the Derby.

Napravnik won the Kentucky Oaks two years ago but her hopes of success on Saturday dampened when her mount drew the inside gate, which has not produced the race winner in over a quarter of a century.

Because of the unusual position of the starting gates for the 1-1/4 mile (2000 meters) journey, horses drawn in the inside are invariably cut off as they approach the rails and shuffled back through the pack but Napravnik was hopeful she could avoid early trouble.

"It's not ideal. I don't think anyone wants the one hole," she said.

"But if I had to have any horse to come out of the one hole, it would be Vicar's because he's real sharp out of the gate and I think we'll be able to get into a good position anyway."

An expected crowd of 160,000 will cram into Churchill Downs while tens of millions of people will watch on television as the race, steeped with tradition including the singing of My Old Kentucky Home and the drinking of Mint Juleps, unfolds.