Say it isn't so, Mo.

Uncle Mo has pulled out of Saturday's Kentucky Derby due to an stomach ailment that has reduced his appetite and energy.

Owner Mike Repole scratched Uncle Mo because he felt he hasn't recovered enough from an intestinal ailment to run in the 1¼-mile race.

Uncle Mo was the 9-2 second choice on the morning line.

There are now just 19 horses in the field for the 137th Derby. Dialed In is the 4-1 early favorite.

The announcement was made by Repole on Friday morning, about 40 minutes before Derby wagering opened.

Uncle Mo won last year's Breeders' Cup Juvenile at Churchill and was undefeated heading into the Wood Memorial.

Todd Repole's colt was soundly beaten in the Wood. He was the leader with a quarter-mile to go, but he wound up 3rd by a length. Shortly after that race, his appetite fell off and raised suspicions. An exam turned up the gastrointestinal tract infection.

Uncle Mo could still run in the Preakness on May 21st. Repole said Uncle Mo could also wait to run him at Saratoga in July.