LOUISVILLE, Ky. — At Classic Empire’s lowest moments, when the early Kentucky Derby favorite was beset by hoof and back ailments and refusing to work, trainer Mark Casse shared a bit of advice with close friends.

“I have a few friends who like to bet in Vegas, and I told them to get all they can get,” Casse recalled. “Because everybody was counting him out, but he was long from done.”

Classic Empire is the once and future king of this year’s Derby field. He was the consensus best 2-year-old of 2016, winning all four races he finished, including the Breeders’ Cup Juvenile. But in the first three months of 2017, he became better known for his health woes and erratic personality than for his race results. Then in the April 15 Arkansas Derby, he was back, roaring from the outside to pass Conquest Mo Money.

On Wednesday, Churchill Downs oddsmaker Mike Battaglia officially made him the 4-1 morning line favorite for Saturday’s Derby. Classic Empire, ridden by Julien Leparoux, will start from the No. 14 post position.

“I still always thought he was the best horse,” Casse said. “I just didn’t come out and say it, because I was taking enough pressure in the press.”

As fascinating as Classic Empire’s rocky story has been, the fact he’s the favorite speaks to the unsettled state of this year’s Derby field. There are plenty of talented horses but none of them arrived here with spotless resumes.

“We all have chances in there,” said trainer Dale Romans, who will saddle 20-1 choice J Boys Echo in the Derby. “I don’t think it’s a weak group of horses. I think it’s an even group of horses.”

Rival trainers view Classic Empire as a gifted horse and legitimate favorite. They just don’t view him as a world beater.

“When you look at it just on numbers, it’s very even,” said trainer Doug O’Neill, who won last year’s Derby with Nyquist and will saddle 20-1 choice Irap in this year’s race. “There’s no horses coming in — there are a lot of really nice 3-year-olds that just look like they’re getting better and better — but no freakish 2-year-olds that have continued on.”

No contender has proven he can handle everything thrown at him.

“It’s even in the fact that you have brilliance lacking experience,” said Hall of Fame trainer Steve Asmussen, who has three horses in the race, including popular handicapper’s choice Hence. “And when you put them all together, we know as horsemen that not everybody’s going to get their best circumstances.”

Irish War Cry is a 6-1 fourth choice in Battaglia’s morning line, and he’ll start from well outside at the No. 17 post. No horse has ever won the Derby from there, but trainer Graham Motion was content with the draw.

“Someone’s going to win from the 17 hole one day,” Motion said. “I was very happy with it. I think it suits the horse, actually. It doesn’t bother me at all.”

Todd Pletcher-trained Always Dreaming and hometown favorite McCraken are the co-second choices at 5-1.

Always Dreaming will start from the No. 5 post, an ideal spot for an inexperienced horse who blew away the field in the April 1 Florida Derby.

McCraken, undefeated in three races at Churchill Downs but coming off a disappointing run in the Blue Grass Stakes, will start from the No. 15 post.

No other horse is better than a 15-1 choice — odds shared by Girvin, Gunnevera, Hence and Gormley — in Battaglia’s early line for the field of 20.

So far, the tumult of Derby week, with hundreds of onlookers crowding the backstretch, has not triggered any of Classic Empire’s personality quirks.

“He is handling it with 100 percent class, as he does 99 percent of the time,” Casse said. “He just takes it in. I think he knows he’s special.”

He won’t go so far as to say Classic Empire’s erratic traits have been overblown.

“Every now and then, he’ll come up with something new,” the veteran trainer said. “But the more and more I think about it, there’s reasons for it.”

For example, when Classic Empire turned hard right to start last year’s Hopeful Stakes, he had banged his ankle on the starting gate, Casse said.

Then when he finished a listless third in the Feb. 4 Holy Bull Stakes and missed five weeks of training, he was coping with a foot abscess and a sore lower back.

“There’s no doubt the stuff that happened in South Florida was from his foot and his back,” Casse said. “Anybody that doubts that just has to watch him train now.”

If anything, he believes in Classic Empire more fervently because the horse has confronted adversity and come out the other side.

Casse saw that quality the first time Classic Empire ran, when he started poorly, had mud kicked in his face and still won easily. In his second race, he turned left out of the gate, appeared hopelessly behind and yet ran down a good horse in Recruiting Ready. His rally in the Arkansas Derby, where he was still arguably undertrained, was only the latest example.

“Good horses win when everything goes their way. Great horses win when nothing goes their way,” Casse said. “Nothing went right (in the Arkansas Derby), and he still won. That race may ultimately be what can make him a winner. A lot of the good horses in the Derby have never had to face any adversity. If they do, let’s see them meet the challenge. We know he’s capable of doing it.”

When Casse was 8 years old, he appeared on an NBC program featuring young entrepreneurs. Asked his life’s goal, he said he wanted to win the Kentucky Derby. Forty-eight years later, with Casse now working beside his own son and assistant, Norman, his zeal for the race has not diminished.

This one is all the more satisfying for the difficulties Classic Empire has presented.

“Just to be here, given the circumstances, is a great accomplishment in itself,” Casse said. “Whatever happens from here is a bonus. We’re just happy to be here.”