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.
Rule 2.00 (Obstruction) Comment: If a fielder is about to receive a thrown ball and if the ball is in flight directly toward and near enough to the fielder so he must occupy his position to receive the ball he may be considered “in the act of fielding a ball.” It is entirely up to the judgment of the umpire as to whether a fielder is in the act of fielding a ball. After a fielder has made an attempt to field a ball and missed, he can no longer be in the “act of fielding” the ball. For example: an infielder dives at a ground ball and the ball passes him and he continues to lie on the ground and delays the progress of the runner, he very likely has obstructed the runner.
It is not obstruction if the ball is in flight directly toward and near enough to the fielder so he must occupy his position to receive the ball. The most common example of fielding a thrown ball is a catcher occupying a position to receive a thrown ball. The qualification "near enough" is usually satisfied if the thrown ball is within the cutout (roughly within 13').
No obstruction - F2 in act of fielding the thrown ball (MLB is very
liberal re: thrown ball obstruction, esp. with plays at the plate)
No obstruction - F2 in act of fielding the thrown ball
No obstruction – F2 in act of fielding the thrown ball
No obstruction - Batter/runner collides with first baseman (incidental – fielder need not disappear)
No obstruction - Fielder blocks base while fielding throw (act of fielding throw)
No obstruction - Collision at 1B, throw into line is train wreck
No obstruction - Collision at 2B, throw into baseline is a train wreck as long as the fielder is fielding a thrown ball and the runner does not intentionally interfere.
A fielder is trying to field a ball when:
(1) position to glove a rapidly approaching ball;
(2) actually gloving a ball;
(3) trying to gain possession of a ball without taking steps; or
(4) throwing a ball. [J/R]