Uncle Mo has a gastrointestinal infection and may be a no-go for the Kentucky Derby on May 7.
The early Derby favorite lost for the first time in the Wood Memorial on Saturday at Aqueduct, finishing third as the prohibitive 1-10 betting choice.
The 2-year-old champion was given blood tests on Tuesday after his poor performance, and veterinarians discovered the infection. Trainer Todd Pletcher and owner Mike Repole were told Uncle Mo could continue training while undergoing treatment.
Pletcher said Thursday he still plans to ship Uncle Mo to Churchill Downs on April 18 and give the colt two workouts before making a Derby decision. However, he added: ''If I do not feel that Uncle Mo is 100 percent for the Kentucky Derby, both Mike and I agree that he will not run.
''My main focus is to return Uncle Mo to optimum health in the next 23 days, and I am optimistic that we can accomplish this goal.''
Uncle Mo won his first four races by a combined 27 lengths, including the Breeders' Cup Juvenile in November. The 3-year-old colt won his first start this year — the Timely Writer Stakes — before finishing behind Toby's Corner and Arthur's Tale in the Wood.
Repole said it's been his ''lifelong dream to run and win the Kentucky Derby.'' But if Uncle Mo is not at his best, ''we will skip the Derby and go right to the Preakness.''
Repole has another likely Derby starter in Stay Thirsty, winner of the Gotham who ran seventh in the Florida Derby.
