David Flores will ride Storm Treasure for trainer Steve Asmussen in the Kentucky Derby presented by Yum! Brands (gr. I), the trainer said Tuesday.Flores, 38, a regular on the Southern California circuit, will have his eighth Derby mount Saturday. Flores' best finish came in his first Derby ride when he finished third on Free House in 1997.Asmussen said he decided not to announce the jockey for Storm Treasure until after both of his Derby candidates had their final breezes Monday morning. "I was just making sure that they both came out of the work well and they were going to run," Asmussen said. "I waited until this morning to see if they were still healthy."Asmussen said that he has used Flores on his horses in the past. "He ran fourth on More Than Regal in the Lane's End (gr. II) for us, most recently," Asmussen said. "He's a quality person, a quality rider."Flores takes over from Mark Guidry, who rode Storm Treasure to a second-place finish in the Toyota Blue Grass Stakes (gr. I) at Keeneland. Guidry is riding Sharp Humor in the Derby.Private Vow, Asmussen's other starter, turned in a bullet 1:00 for five furlongs Monday morning. Storm Treasure had the second-fastest time at the distance, 1:00 2/5."I'm very pleased," Asmussen said of his two colts as Saturday's race approaches. "I have the same concerns: can one of them (Private Vow) go far enough and if the other one (Storm Treasure) is fast enough."