LOUISVILLE, Ky. -- The pockmarked road to the Kentucky Derby claimed another victim Friday when Uncle Mo was scratched due to a mysterious stomach ailment, further dimming a race already short on star power and speed.
Uncle Mo's defection also threw the Derby wide open.
"You're never safe until you put that saddle on because anything can happen," Hall of Fame trainer Bob Baffert said.
Owner Mike Repole announced the decision to scratch second favorite Uncle Mo about 40 minutes before wagering opened for the 137th Derby, set for Saturday at 6:24 p.m. EDT. The colt has been bothered by a stomach problem, but vets couldn't find a reason for his decreased appetite, energy and poor-looking coat.
"I'm actually relieved and now I'm really concerned and worried about Uncle Mo," Repole said. "My hope is Uncle Mo gets healthy. He is a superstar."
Uncle Mo's absence reduced the already less-than-dazzling field to 19 horses, with Dialed In as the 4-1 favorite for two time-winning trainer Nick Zito.
Already lost in one of the flukiest Triple Crown seasons in memory were Premier Pegasus, The Factor, Jaycito, To Honor and Serve and Toby's Corner, among others.
Saturday marks the 20th anniversary of Zito's first Derby victory, when Strike the Gold came from off the pace in 1991.
Dialed In, who won his debut at Churchill Downs in November, shares a similar running style.
"He's a closer and that's the way he needs to run," Zito said. "There are four or five horses that look good, but you have to beat all of them."
Dialed In won the Florida Derby in a woefully slow time -- and that was no exception. The speed figures used to rate a horse's past performance indicate this year's crop of Derby contenders is lacking in zip.
"Slow, fast or in-between, as long as he gets the distance what do we care?" Zito said. "If he does what we ask him to do, what's the difference really?"
Arkansas Derby winner Archarcharch posted the highest speed figure in the major Derby preps, but will have a difficult time duplicating that coming out of the troublesome No. 1 post on the inside rail.
The uncertainty hovering over the race dovetails with a messy run-up that saw a slew of contenders sidelined by injuries and poor performances.
"There's so much parity," said Baffert, a three-time winner who will saddle Midnight Interlude, who will try to buck history to become the first horse since Apollo in 1882 to win without having raced as 2-year-old.
"When you have a lot of equal horses and there's no standout, everybody thinks, 'Well, maybe it's not that tough of a field,' but I think it's a tough field," he said.
Without Uncle Mo, Repole and trainer Todd Pletcher still have a shot at winning with Stay Thirsty, who will try to rebound after fading to seventh in the Florida Derby.
Comma to the Top, Shackleford and Soldat figure to be among the early pacesetters. Soldat could benefit most if the race-day forecast of a 60 percent chance of rain holds since he trained well over the sloppy dirt track earlier in the week.
"Soldat is going to be tough on the outside," Baffert said. "He's got me a little worried, along with the 18 others."
Nehro, who's won once in five starts, will try to end trainer Steve Asmussen's 0-for-9 skid.
Animal Kingdom, Brilliant Speed, Comma to the Top, Derby Kitten, Irish import Master of Hounds, and Twinspired are inexperienced on dirt, having mostly raced on synthetic surfaces or turf.
Calvin Borel, who has won the Derby three times in the last four years, will try to become the first jockey to win three in a row aboard Twice the Appeal.
Three women have a chance to make Derby history. Kathleen O'Connell, who oversees Watch Me Go, and heart transplant recipient Kathy Ritvo, who saddles Mucho Macho Man, will try to become the first female trainer to win. Rosie Napravnik, aboard Pants On Fire, will try to be the first female jockey to land in the winner's circle.
With 19 horses set to start, the purse is $2,171,800, with the winner earning $1,411,800. Without Uncle Mo, who drew the No. 18 post, Nehro and Watch Me Go move one spot in the starting gate, leaving the No. 20 hole empty.