Royal Mo suffered a career-ending leg injury Sunday morning at Pimlico Race Course while training for Saturday’s Preakness Stakes. The 3-year-old colt fractured his inside right front sesamoid bone and was taken by ambulance to the University of Pennsylvania’s School of Veterinary Medicine’s New Bolton Center in Kennett Square, Pa.

Jockey Gary Stevens, who took a red-eye flight Saturday from California, pulled up the colt in the stretch during a scheduled 5-furlong workout. The injured leg was equipped with bandages and a splint before the horse was transported by equine ambulance to Pimlico’s stakes barn, where X-rays revealed the fracture.

“There isn’t any other damage,” trainer John Shirreffs said, “so that’s a very good thing for him, for his life after racing.”

The Daily Racing Form reported that Shirreffs said he thought surgery was unlikely, and that the colt would be evaluated and monitored at the clinic.

Maryland-based veterinarian Dr. Dan Dreyfuss told the Form: “This is absolutely a career-ending injury. He is done as a racehorse. If there are no complications, from a life standpoint he should be OK.”

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Stevens said he heard a “pop” while they raced outside a workmate. The 54-year-old Hall of Famer immediately dismounted and held the injured leg while Shirreffs came down from the grandstand, where he had been watching the workout.

“Thankfully, when he went, I had a hold of him,” Stevens said. “He looked out for me and I looked out for him and he pulled himself up.

“The track was perfect. It’s just one of those deals.”

Royal Mo was ready to run in the Kentucky Derby on May 6 but did not draw in from the also-eligible list. Shirreffs was optimistic about his chances in the Preakness.

“It’s very difficult,’’ said Shirreffs, a 1964 graduate of Paul D. Schreiber High School in Port Washington. “Our hopes and dreams were with Royal Mo. Mr. and Mrs. Moss and my wife, Dottie, and I were excited to see him run. We’re all obviously devastated.”