Todd Pletcher is going after the Kentucky Derby with numbers again.

The trainer who has won America's greatest horse race will saddle four horses. Little-known Mike Maker has three starters.

Art Sherman has just one. But it's a really good one.

California Chrome is the favourite for the 140th Derby on Saturday. The colt brings a four-race winning streak into Churchill Downs, having won those by a combined 24 1/4 lengths.

"I've never had a horse that did that before," said Sherman, who began training in 1980 after being a jockey for 21 years and later a racing official. "I just want my horse to have a fair shake at it and have good racing luck, and I'm sure hopeful for him. He's a gutty little horse."

Pletcher knows something about luck.

Four years ago, he ended a winless run with his first 24 entries when long shot Super Saver, one of four horses he entered, won under a rail-hugging ride by Calvin Borel.

That was the year Pletcher had the favourite, Eskendereya, who was forced to drop out six days before the Derby with a leg injury. He also had the horse to beat in 2011, Uncle Mo, who was scratched with a stomach ailment on Derby eve.

This year, Pletcher's quartet is made up of Arkansas Derby winner Danza, Risen Star winner Intense Holiday, Spiral Stakes winner We Miss Artie, and Vinceremos, who finished 14th in the Blue Grass.

California Chrome will need some luck in a field of 19 horses for the 1 1/4-mile (2,400m) race at Churchill Downs. California Chrome drew the No.6 post. Only two horses have won from there, most recently Sea Hero in 1993.

Maker's trio of contenders is Louisiana Derby winner Vicar's in Trouble, General a Rod and Harry's Holiday.

"I feel my horses they can adjust to whatever the pace calls for," he said.

Maker has had five previous Derby starters, including Hansen, who was ninth in 2012. Both he and Pletcher are former assistants to Hall of Fame trainer D. Wayne Lukas, a four-time Derby winner.

Vicar's in Trouble will be ridden by Rosie Napravnik, who will try to become the first female jockey to win the Derby. Her husband, Joe Sharpe, is an assistant to Maker.

Last year, Napravnik rode Mylute to a fifth-place finish in the Derby behind Orb and a third-place finish in the Preakness Stakes behind Oxbow. Those were the best by a female rider in each race.

Sherman is going for a bit of history himself.

The 77-year-old could become the oldest trainer to win, surpassing Charlie Whittingham, who was 76 when Sunday Silence won in 1989.

Three-time Derby winner Bob Baffert had two contenders, until second favourite Hoppertunity was scratched on Thursday because of a sore left front foot. Baffert said the colt could return in time for the Preakness on May 17.

The scratching brought Pablo Del Monte into the field, however the owners of the 50-1 shot turned down the chance on Friday, preferring to wait for the Preakness.

Baffert's other horse was 20-1 shot Chitu.

Wicked Strong, the colt named for the victims of last year's Boston Marathon bombings, replaced Hoppertunity as the early second choice at 6-1.

Steve Asmussen trains fifth favourite Tapiture, the Southwest Stakes winner.