Obstruction call on the Sox 3rd baseman on an inaccurate throw from the catcher in trying to gun down Craig, who is sliding into 3rd. Ball sails into left field, the Sox 3rd baseman is on the ground, belly side down, his legs go up, Craig picks himself up from his slide into 3rd, trips on the 3rd baseman's legs, and the ump calls "obstruction" which is this rule:
OBSTRUCTION is the act of a fielder who, while not in possession of the ball and not in the act of fielding the ball, impedes the progress of any runner..
Intent does not matter.