Player gets hit by ball in a rundown. Baseball?

Out of Pure curiousity I was just wondering. If a player gets in a rundown or pickle, and the infield players are doing the defense drill for it, and the player is hit by a thrown baseball, and falls to the ground or is knocked out. What happens? What if it was Intentional, and what if it was accidental? Any rulings? and if he's knocked out and tagged, and it was intentional or not. Is he seriously out?