By Jay Privman at DRF…

The run-up to this year’s Kentucky Derby has been punctuated by a series of favorites being defeated in major prep races, defections of previously well-regarded horses, and some surprising additions. That trend continued in the past 48 hours, beginning on Saturday with upsets by Brilliant Speed in the Blue Grass Stakes and Archarcharch in the Arkansas Derby – as well as the defeat of heavily favored The Factor in the Arkansas Derby – and continuing Monday, when the European colt Master of Hounds was announced as a likely starter in the race, and Astrology, one of last year’s elite 2-year-olds, was withdrawn from consideration.

Combine that with the uncertainty hanging overUncle Mo, who arrived at Churchill Downs on Monday, and this Derby is as stormy as the rainclouds that have settled over the commonwealth of Kentucky in recent weeks.

There are still more twists and turns likely to unfold. Less than three weeks before the May 7 race, the only certainties are that Dialed In has emerged as the favorite, and more than 20 horses still want to run in the Derby, meaning graded stakes earnings likely will once again come into play.

Graded stakes earnings are used to determine the field if more than 20 horses enter the race. Those near or just below the bubble will be keenly watching developments with horses such as J P’s Gusto and The Factor, who are currently in the top 20 and have yet to be officially ruled out of the race, though neither is expected to run. More significantly, both Uncle Mo and Jaycito have had issues to deal with recently. If they were to come out, that would open up more spots.

Uncle Mo, once the heavy Derby favorite, was found to have a gastrointestinal infection following his first loss, in the Wood Memorial on April 9. He will continue to be treated, and, though scheduled to work twice at Churchill, beginning this Sunday, may have that schedule pushed back depending on how the treatment is going, his trainer, Todd Pletcher, said Monday.

“With that type of thing, I don’t think you expect an overnight miracle. I think it’s something that we’ll see gradual improvement,” Pletcher said just after Uncle Mo left Belmont Park, bound for Kentucky, where he joined another Pletcher-trained Derby contender, Stay Thirsty.

“I think he and every horse pointing for the Kentucky Derby the next 19 days has to do really well – him, Stay Thirsty, and everybody else that’s pointing to it,” Pletcher said. “The next 19 days are absolutely critical. You have horses that move forward a lot in that amount of time, or they can be off the trail on any given day. That applies to everybody.

“I think if he trains accordingly, I still feel like he’s the best horse that’s going to run in the Kentucky Derby if we can get him back to his best performances. I haven’t seen anybody that’s run a better race than his Breeders’ Cup Juvenile. We just have to get back to that level.”

Jaycito, scheduled to run in the Coolmore Lexington Stakes on Saturday at Keeneland, has been battling a sore foot. Also in the top 20 is Watch Me Go, whose status is uncertain following a poor try in the Illinois Derby.

Cash will not be a concern for Archarcharch or Brilliant Speed, who secured berths in the Derby with their wins on Saturday. Archarcharch got a Beyer Speed Figure of 98 in the Arkansas Derby. Brilliant Speed got a 93 in the Blue Grass.

Archarcharch emerged from his win in excellent shape, his trainer, Jinks Fires, said the morning after the race. He was scheduled to be sent by van from Arkansas to Churchill Downs on Monday night.

“If they don’t block the road we’ll be there,” said Fires, a trainer for 50 years who at the age 70 will have his first starter in the Derby.

“I always wanted to go there with a horse I thought had a shot. And we do think we have a shot,” he said.

It was the first Grade 1 win for Fires, who is part of a noted racing family. His brother is Hall of Fame jockey Earlie Fires. Jinks Fires’s son-in-law, Jon Court, rode Archarcharch.

Nehro, the Arkansas Derby runner-up, is also bound for the Kentucky Derby, according to his trainer, Steve Asmussen.

Asmussen also trains Silver Medallion, who likely will run in the Lexington to try and move into the top 20 in graded earnings. Asmussen’s other Derby contender, Astrology, is being re-routed to the Jerome on Saturday at Aqueduct, which could set him up for a potential start four weeks later in the Preakness Stakes, the second leg of the Triple Crown, May 21 at Pimlico.

In the Blue Grass, the inch or two that separated the victorious Brilliant Speed from runner-up Twinspired might be the difference in which horse makes the Derby field. Brilliant Speed earned a first prize of $450,000, whereas the $150,000 earned by Twinspired – which brings his graded stakes total to $197,500 – has him near the bubble, and that’s before the Lexington is run.

Master of Hounds, second most recently in the United Arab Emirates Derby, is being strongly considered for the race, an Irish-based spokesman for Coolmore Stud’s John Magnier, who owns Master of Hounds, said Monday.

“At the moment, the plan is for Master of Hounds to run in the Derby,” said the spokesman, who asked not to be identified but has spoken with authority on Coolmore-related matters in the past. “He still has a few pieces of work. After that, the trainer will decide.”

Master of Hounds, a son of Kingmambo, is trained by Aidan O’Brien, whose last Derby representative was Johannesburg, who finished eighth in the 2002 Derby.

Master of Hounds is currently at Ballydoyle in Ireland. No decision has been made on when Master of Hounds would ship to the United States, or who would ride him in the Derby, the spokesman said.

Several other riding assignments are in flux. Santiva will need a new rider, since Julien Leparoux rides Dialed In. Comma to the Top would likely need a new rider if he runs, since Corey Nakatani is expected to stick with Nehro.

Among those still available are Calvin Borel, who has won the Derby three times in the last four years, and Ramon Dominguez, last year’s Eclipse Award winner.

One riding assignment likely firmed up is that of Robby Albarado, who will work Spiral Stakes winner Animal Kingdom on dirt on Saturday at Churchill Downs, a drill that is expected to determine Animal Kingdom’s status for the Derby.

“We wanted Robby to work him because he won on him at 2 and he has breezed him in the past,” Barry Irwin, the president of owner Team Valor International, said Monday. “This way, we can get the best possible line on whether the colt can act on the Churchill Downs main track.”