One year after benefiting from a bizarre and controversial (although I believe correct) Infield Fly call in the NL WIld Card, the St. Louis Cardinals won Game 3 of the World Series on an obstruction call on the Red Sox third baseman (video embedded). Although early reaction (at least outside the Red Sox clubhouse) seems to approve of the call, this one will remain a point of contention, both because it occurred in the World Series and because it allowed the game-winning run to score (officially, it was scored an error on the third baseman who obstructed).
Rule 2.00 of the Official Baseball Rules defines "Obstruction" as "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." A Comment to the rule provides that a fielder can occupy space when "in the act of fielding a ball," but once he has attempted to field a ball and missed, he can no longer be in the act. Thus, if a player dives at a ball and continues to lie on the ground after it is passed him and delays the runner's progress, "he very likely has obstructed the runner." The rule has no intent requirement; impeding the runner, even unintentionally, constitutes obstruction. Under R. 7.06(b), the umpire can "impose such penalties, if any, as in his judgment will nullify the act of obstruction;" typically, that is the base he would have been entitled to without the obstruction.
Here is video of the umpires' press conference, which can best be described as a judicial opinion issued from the bench, explaining a decision. A couple of themes emerge that, I think, support the call. First, intent does not matter, only the result. Even if (as here) it is almost unfair because the play happened too quickly for the fielder to do anything to get out of the way. Second, while the internet is talking about the Sox third baseman's legs going up in the air, the umpires insisted that it was not the legs, but the fielder's body that created the obstruction. Third, it did not matter that the runner was inside the foul line when he tripped over the fielder (one ump said he was right on the chalk, the video suggests he was inside the line), a point the Red Sox players kept repeating in interviews; a runner can "make his own baseline" by picking the most direct path to the next base.
As expected, some players (Sox starter Jake Peavy was one) complained about the game ending on the umpire's call and the umpire "deciding" the game, a reflection of what Mitch Berman has called "temporal variance" in enforcement of sports rules. That argument seems especially incoherent in this context. After all, the Cardinals could just as easily argue that the play was important precisely because the Cardinals had a chance to score the game-winning run and the Sox were preventing him from doing so.
Anyway, obstruction now will be the word of the rest of this Series.