INGLEWOOD, Calif. - Corey Nakatani, who was scheduled to ride in the Kentucky Derby on Saturday, sustained a "slight concussion" Thursday in a spill at Hollywood Park and will be sidelined until next week. The injury prevented Nakatani from riding Blue Burner in the Derby; he was replaced by Pat Day. Nakatani went down in the third race when his mount Whirlwind Trip clipped heels with Star Nine, the eventual winner ridden by Tyler Baze.