Champion UNCLE MO (Indian Charlie) was withdrawn from the Kentucky Derby (G1) Friday morning, a development that was not altogether unexpected.

Owner Mike Repole and trainer Todd Pletcher had been indicating that if they weren't certain that the colt was 100 percent, they would not race him in the 1 1/4-mile classic.

Uncle Mo has been treated for a gastrointestinal track problem since shortly after his third-place finish as the stout favorite in the April 9 Wood Memorial (G1), which came as his first career loss. He has received antibiotics as part of his treatment.

"We took him off his meds the past few days coming up to the race and he hasn't done as well since," Pletcher said. "He's got one specific enzyme that's elevated that has everyone baffled, they can't identify why. Generally, without getting too scientific, when this particular enzyme is elevated there is also something in the bloodwork that would lead them to the direction toward a liver or a kidney, but this specific case it's one single enzyme that's elevated that doesn't really lead you anywhere else.

"The real problem here is that we're in a gray area. It just isn't clear. We're not sure what it all means. I just don't feel that this horse is right. The Wood was the first tip off to that. When he ran the way he did, we knew something wasn't right. We've been trying to figure out what since.

"The biggest thing I see is depressed appetite, loss of weight and his haircoat's not right," Pletcher noted. "I told Mike that this decision will stink on May 7. But later in the year -- when they run the Jim Dandy (G2), the Travers (G1) and the Breeders' Cup Classic (G1) -- maybe it will be the right decision."

Repole noted that his colt had trained well at the track as recently as last Sunday, that he continued to do well in his gallops, but that something still "just was not right" with the three-year-old.

"We had three vets (Dr. Doug Byers, Dr. Steve Allday and Dr. Ken Reid) go over him (Thursday)," Repole said. "But after they left, Todd said 'I don't want to run this horse.' The vets didn't say the horse couldn't run; in fact they said he could. But when Todd said he didn't want to run, that was pretty much it for me. I know he treats these horses better than he treats his own health and if he didn't want it, then that was that."

Repole said in his thinking process the three vets had one vote, Pletcher had another and he was the third. He sided with his trainer and the decision was made.

Pletcher, who had to scratch the Kentucky Derby favorite in Eskendereya last year during Derby Week, was obviously downcast at the latest development with a horse he called "the best I've ever trained."

"I am very, very, very, very disappointed about this," Pletcher said. "I don't think I've ever had a horse as good as Uncle Mo. We've had every resource to try to get this horse right, but we're not there. I take this as a personal failure. We just don't know what's wrong with this horse and it scares me. I feel very sorry for Mike. I feel very sorry for Johnny Velazquez. This is the third year in a row he's lost the Derby favorite."

Last year, Hall of Fame candidate Velazquez was scheduled to ride Eskendereya in the race and in 2009 he had the call on Quality Road (Elusive Quality), who appeared to be the Derby favorite prior to being withdrawn because of injury. Velazquez will now take the mount on ANIMAL KINGDOM (Leroidesanimaux [Brz]). He replaces Robby Albarado, who was injured in a post parade incident at Churchill on Wednesday.

Both Uncle Mo and STAY THIRSTY (Bernardini) put in gallops of 1 1/4 miles Friday morning at about 6:10 a.m. (EDT) at Churchill. Uncle Mo had his regular exercise rider, Hector Ramos, aboard, while Gotham S. (G3) winner Stay Thirsty was handled by his regular morning man, Fernando Espinoza. Stay Thirsty will break from post position 4 Saturday and be handled by Ramon Dominguez.

"We're really lucky to still have Stay Thirsty for the race," Pletcher added. "But Uncle Mo was the franchise."

Pletcher also said that Uncle Mo could not be called officially out of training, but that they would make no further plans for the colt "until we get a proper diagnosis."

Repole, the irrepressible New York businessman who is heavily invested in the racing game and feels that he's got the horse of a lifetime in Uncle Mo, spoke further of his disappointment.

"Todd didn't like his weight, his energy, his coat," he said. "We brought in the best vets you can get and they are baffled. We can't find an answer."

Repole has brought in 95 friends and family from New York for the Derby and said he was happy to have them with him going through this hard time.

"We had a wonderful dinner with everyone at a restaurant in town last night and it was good," he stated. "Family is important."

Repole said that Thursday morning at about 10:30 a.m., after the vets had offered their opinions and he heard from Pletcher, he all but made the decision to scratch. He said they waited to see some test results, but that his path then was clear.

"I was actually relieved (that they were not going to run Uncle Mo)," the owner said. "I know I'm lucky I've got another horse to run in the race and we'll hope he can step up. But our thoughts are with Uncle Mo. We want to find out what's wrong with him and get him right; get him back.

"We are not worried about his race schedule. We don't know what's wrong with him and we're worried about the horse."