ARCADIA, Calif. — Kentucky Derby runner-up Pioneerof the Nile has been retired with a soft-tissue injury in his left front leg.

Trainer Bob Baffert said the injury was discovered at Santa Anita on Sunday morning when the 3-year-old son of Empire Maker came off the track.

A scan determined a small hole in a tendon. While there's a chance the horse could have returned to racing in 6-8 months, there was no guarantee that he would remain healthy. Baffert advised owner Ahmed Zayat it wasn't worth the risk.

"It's devastating," said Baffert. "I'm still in denial. He's a star. He put me back on the Triple Crown map."

Pioneerof the Nile became one of the Derby favorites by winning four straight prep races in California. All of those wins — including the Santa Anita Derby — came over synthetic surfaces, but he remained a solid third choice behind Friesan Fire and Dunkirk in the mud at Churchill Downs.

Baffert thought for a moment he had his fourth Derby winner when Pioneerof the Nile took the lead at the top of the stretch, but Mine That Bird blew by along the rail. He settled for second after holding off Musket Man by a nose.

"He was a scrapper," Baffert said. "He always did what he needed to do."

Pioneerof the Nile couldn't bounce back in the Preakness, finishing 11th. Baffert returned the horse to California and had him pointed toward the Swaps Stakes at Hollywood Park on July 18, with an eye on the Breeders' Cup Classic in November if things went well.

"He was getting stronger," Baffert said. "He's changed so much since the Derby. But the only positive thing about it is at least we got this far with him. If it had happened three days before the Santa Anita Derby, I'd be vomiting."

Pioneerof the Nile finished with five wins in 10 career starts and $1,634,000 in earnings.