LOUISVILLE, Ky. — Suddenly, the Kentucky Derby is wide open.
Favorite Omaha Beach was scratched because of a breathing problem Wednesday night, leaving a pair of Hall of Famers on the sideline — trainer Richard Mandella and jockey Mike Smith.
Churchill Downs oddsmaker Mike Battaglia revised the morning line to make Game Winner the 9-2 favorite for the 1¼-mile race Saturday.
Improbable and Roadster were installed as the co-second choices at 5-1, giving five-time Derby-winning trainer Bob Baffert the top three choices in the 20-horse field.
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Mandella said Omaha Beach developed a cough and a subsequent veterinary exam showed the colt has an entrapped epiglottis. It’s generally not life- or career-threatening and is typically corrected with minor surgery.
‘‘It’s been a devastating thing, but we have to do what’s right for the horse,’’ said Mandella, who has never won the Derby with six previous starters.
The trainer said Omaha Beach will have surgery in Kentucky in the next few days and will be sidelined for two to three weeks. The ordeal will knock him off the Triple Crown trail.
‘‘It’s such a disappointment, but we’ll fight again,’’ Mandella said. “We won’t be out a long time.’’
The scratch was another blow to cancer survivor Rick Porter, the colt’s 78-year-old owner. He has twice finished second in the Derby, in 2007 with Hard Spun and the following year with filly Eight Belles, who broke her ankles past the finish line and had to be euthanized.
‘‘He’s a great sport,’’ Mandella said. ‘‘I've got very good support.’’
Omaha Beach had been the 4-1 early favorite.
Mandella’s dry sense of humor came out when he said, ‘‘My wife has my leg tied down so I can’t jump out of the window.’’
Smith had chosen to ride Omaha Beach instead of Roadster and now he won’t have a chance to win the Derby for the second straight year. He rode Justify to victory last year.
‘‘I'm a little bummed out, but the horse is OK and we’re going to be all right,’’ Smith told the AP by phone. ‘‘The good news is it wasn’t anything that is life-threatening.’’
Smith has three mounts on Friday’s card at Churchill Downs and five Saturday.
‘‘I'll be rooting for Roadster’s connections big-time,’’ he said. ‘‘I'll be a glorified cheerleader.’’
Omaha Beach galloped Wednesday morning without problem and Mandella said everything was fine. But that changed by late afternoon when the exam showed the cough was more than a minor irritation.
The condition can indicate the start of a virus, a sore throat or a sore in somewhere in the horse’s soft palate.
Omaha Beach’s scratch moves Bodexpress into the field in the No. 20 post.
Mandella said he would likely return to Southern California before the Derby.
‘‘I didn’t lose interest,’’ he said, ‘‘but I don’t want to be here and watch it.’’
It’s not the first time the Derby has lost a favorite leading up to the race.
In 2009, I Want Revenge became the first morning-line favorite to scratch the day of the race because of a hot spot on his ankle.