Game 3"s Decisive Play - Why Call Was Obstruction - NYTimes.com You think baseball is not intricate? Consider the difference between "interference" and "obstruction." The dictionary says that in some cases, the words are interchangeable. But not in baseball. The play that ended the third game of the World Series on Saturday - when the umpires ruled that Will Middlebrooks, the Boston Red Sox" third baseman, had impeded the progress of Allen Craig, the St. Louis Cardinals" base runner, allowing Craig to score the winning run - was a case of obstruction, which only a defensive player can commit. Didn't know that? Neither, apparently, did the the play-by-play summary of the game, which said Middlebrooks had committed an "interference error." But interference is a whole other thing. Generally, it is an infraction by the offense - a runner on first plows into the second baseman who is trying to field a grounder, for example. The rule-book definition of interference has four sections. A defensive player commits interference if he hinders the hitter from swinging at a pitch (almost always because the swing clips the catcher's glove). Spectators commit interference by reaching into the playing field to snatch a souvenir ball from a waiting fielder. Even an umpire can commit interference: if he gets in the way of a catcher making a throw; or if he's hit with a batted ball in fair territory before it touches a fielder; or before the ball passes a fielder other than the pitcher. Of course, obstruction and the kind of interference committed by a runner are both about hindrance, which is why Saturday's decisive play calls to mind the 1975 World Series, in which the Cincinnati Reds defeated the Red Sox in seven games. In the bottom of the 10th inning of Game 3, the Reds had a man on first with no one out when the hitter, Ed Armbrister, laid down a bunt in front of the plate. As he left the batter's box, Armbrister tried to avoid catcher Carlton Fisk but briefly got in his way. Fisk's throw to second sailed into center field, and the Reds went on to win. The plate umpire, Larry Barnett, was vilified for not calling interference. He said later that the contact was incidental and that Armbrister had as much right to run to first as Fisk had to make a play on the ball. In 2007, Referee magazine called Barnett's decision one of the 18 greatest calls in sports officiating. And in fact there is a line in the rule book that covers this precise situation: "When a catcher and batter-runner going to first base have contact when the catcher is fielding the ball, there is generally no violation and nothing should be called." Fans who say the Sox never get a break on this obstruction/interference business forget Game 3 of Boston's five-game division series win over the Oakland Athletics in 2003. In the second inning, Boston catcher Jason Varitek was caught in a rundown between third and home and ran into third baseman Eric Chavez, who was called for obstruction. The umpires allowed Varitek to score even though he was heading back to third when the collision occurred. Chavez was guilty of Type A obstruction, an infraction that occurs when a play is being made on the runner. The remedy is that the runner is awarded at least the next base. In another break for the Red Sox, in the sixth inning of that game, the umpires called Miguel Tejada of the A's out at the plate even though he was obstructed on his way around third by Bill Mueller. Because there was no play being made on Tejada at the time, this was a Type B obstruction, which means the umpires must determine whether the obstruction prevented the runner from advancing safely. Bruce Weber is the author of "As They See "Em: A Fan's Travels in the Land of Umpires."