Top Kentucky Derby contender McKinzie has sustained an injury and won't start in the Santa Anita Derby, trainer Bob Baffert said a few minutes after the Dubai World Cup on Saturday night in Dubai.

Missing the Santa Anita Derby obviously could put McKinzie's status for the Kentucky Derby in doubt.

Baffert said it was unclear how McKinzie hurt himself and even what the exact nature of the injury is. McKinzie worked a strong five furlongs on Monday at Santa Anita but didn't come out to train Thursday.

"We don’t know if he did it in the stall or what, because he was fine," said Baffert, who has been in Dubai since Sunday night. "They noticed he was a little bit off. He didn’t go to the track. The X-rays are clean. Ankles look good, hocks - something came up high [on the leg] on the nuke scan. When he got back he 100-percent jogged fine. I don’t know what it was but we’re being very cautious. It’s day by day, week by week."

With McKinzie scheduled to race in the Santa Anita Derby, the exciting prospect Justify, who has won his first two starts in eye-catching fashion, was to make his stakes debut in the Arkansas Derby. With McKinzie sidelined, Justify becomes a candidate for the Santa Anita Derby.

"It depends how he breezes Monday," said Baffert, who departs Dubai for California early Sunday morning.