Historically speaking, this is nothing new. In the last 30 years, only four morning-line favorites — Fusaichi Pegasus in 2000, Smarty Jones in 2004, Street Sense in 2007, and Big Brown in 2008 — have won the Run for the Roses.

Uncle Mo, the 2-year-old champion who came into the Derby season lightly raced but highly regarded, has not been fit since a stunning third-place finish April 9 in the Wood Memorial at Aqueduct. That Uncle Mo was scratched by trainer Todd Pletcher and owner Mike Repole was not a surprise, but there were those who doubted a healthy Uncle Mo’s ability at the Derby’s 1 1/4-mile distance.

Pletcher and Repole explained the rationale behind their decision to scratch Uncle Mo, who has lost more than 70 pounds in the last month and may have more than the gastrointestinal inflammation that developed after the Wood. Pletcher sounded uncertain when asked if the horse who dominated the 2-year-old circuit would run again.

“We’d like to think so,’’ said Pletcher, who said the doctors were not sure about Uncle Mo’s illness. “We’ve got something going on inside that I don’t know what it is. The best vets in the world don’t know what it is. When you don’t know, that’s when I get scared.

“The next step is go get to the root of the issue. Right now, we have no race plans. Period.’’

Repole sounded equally uncertain.

“This horse has had every resource available trying to figure out what’s wrong with him,’’ Repole said. “And we still can’t figure it out. It was an easy decision. I’m not worried about his racing career. Now we’re really worried about the horse.’’

With Uncle Mo out, Dialed In, whose aggressive, come-from-behind style served him well in the Florida Derby, becomes the people’s choice. With a team of Hall of Fame trainer Nick Zito and highly respected jockey Julien Leparoux, Dialed In is a legitimate favorite, but there is little “wow factor’’ with the son of Mineshaft. Nor is there with any of the other horses.

One resource horse players use in determining betting choices in major stakes races is Beyer Speed Figures, with a figure of 100 regarded as the minimum for legitimate Derby contenders. With Uncle Mo gone, only one horse in the field, Soldat, has posted a Beyer figure in triple figures.

There is also the Borel factor. Jockey Calvin Borel has ridden the rail to victory in the last two Derbies. Tomorrow, Borel is riding Twice the Appeal, who under normal circumstances would probably be 50-1, but with Borel aboard is starting at 8-1 from the No. 3 post.

And then there is the weather. It has been an usually wet spring in Kentucky, drying out only in the last few days, but rain again is forecast for today, specifically this afternoon, which creates more uncertainty.

Which brings us back to Soldat, who loves wet tracks and turned heads with a win in the Fountain of Youth. However, he had heads shaking after a dismal effort in the Florida Derby, the first time he had finished worse than second.

“It was just the trip and the draw [inside post], a hot day, and a dry track,’’ said trainer Kiaran McLaughlin. “So we licked our wounds and came on. He’s great, ready to go.’’

Mark Blaudschun can be reached at blaudschun@globe.com.