LOUISVILLE, Ky. Silent Tactic became the first horse to scratch from the Kentucky Derby on Thursday, putting Great White into the 20-horse field.Mark Casse, the trainer of Silent Tactic, told the Daily Racing Form that the horse was suffering from a minor foot bruise and would be pointed toward the Preakness on May 16.Silent Tactic, who was 20-1 on the morning line, has finished first or second in all six career starts. He registered a pair of runner-up finishes in the Arkansas prep races, including a second to Kentucky Derby favorite Renegade in the Arkansas Derby.His replacement, Great White, is a tall, striking gray colt out of the John Ennis barn who finished fifth place, beaten by 22 lengths, by Further Ado in the Blue Grass Stakes. He earned the bulk of his Derby qualifying points the race prior, winning the Bettaglia Memorial by a neck over Fulleffort, who is also in the Kentucky Derby field.Alex Achard was named to ride Great White, who is 50-1 on the morning line. He will wear saddle cloth No. 21.Silent Tactics defection makes Ocelli, who has not won yet in six career starts, the next in line if a horse scratches between now and Friday morning when the field is locked in.