Here's CBSSportsline take on it:
" Hamilton sustains wrist injury
Josh Hamilton, CF CIN
News: A sprained wrist forced Cincinnati Reds outfielder Josh Hamilton to leave for a pinch-hitter in the third inning of a game against Arizona on Saturday night. Hamilton hit a grounder to Stephen Drew in the first inning, reaching safely on the shortstop's fielding error. He winced after he crossed the base but stayed in the game. When it came time to bat again, he headed for the trainer's room instead. The Reds said he'd have a cast put on the wrist, and it will be examined again during the All-Star break."
Hmm, looks like the injury occurred on the base path at least...not in the batters box