The 4-year-old was scratched after being examined by the Breeders’ Cup Veterinary Panel.
"They (the veterinarians) came back to the barn and they looked at her again. They were not happy with the way she was moving and said they would not allow her to run today," trainer Tony Dutrow said.
Dutrow was understandably disappointed.
"I am sure that whatever is wrong with Rightly So, we will get to the bottom of it and take care of it and then go on from there," he said. "It’s disappointing, but this is all part of the game.