Obstruction isn't always that easy and clear cut......here's 2 examples from MLB:
Under OBR, there are two types of obstruction. In umpire parlance, they refer to them as Type A and Type B obstruction. It gets these names because the applicable rules are 7.06(a) and 7.06(b).
In a nutshell, the rules regarding Type A obstruction REQUIRE the umpire to kill the play and to award the batter AT LEAST the next base. Type A obstruction occurs whenever a play is being made on the runner at the time of the obstruction. (Examples - A runner trapped in a rundown is obstructed by a fielder -or- a runner attempting to steal is obstructed by a fielder while the catcher is making the throw)
Type B obstruction involves plays where a runner has been obstructed, but there was no immediate play being made on the obstructed runner at the time. In this case, the umpire keeps the ball live and only awards the runner those bases he would have obtained (in the umpire's judgment) had the obstruction not occurred.
So, if the ball was already retrieved by the outfielder and was being thrown toward 2nd base in order to stop the runner's advance at the time of the obstruction - this would be Type A obstruction and the umpire would be compelled to award the runner 2nd base, whether the runner would have made it or not.
If the ball was still being chased by the outfielders at the time of the obstruction, this would be Type B obstruction and the umpire can award the batter anything he thinks he would have obtained had the obstruction not occurred.
Game #3 of the 2003 ALCS between the Red Sox and the A's, oddly enough, featured BOTH types of obstruction.
Jason Varitek, of the Red Sox, got caught in a rundown between 3rd and home. While attempting return to 3rd, he bumps into an A's fielder who did NOT have possession of the ball. Obstruction is called by 3rd base umpire Bill Welke. He immediately killed the play and awarded Varitek home.
Later in the game, Tejada attempted to score from 2nd base on a ball hit into left field. Tejada was obstructed by the Red Sox 3rd baseman. Bill Welke called the obstruction but, since the ball was still rolling toward the left fielder, he allowed the play to continue because no immediate play was being made on Tejada.
Tejada apparently heard the umpire's obstruction call and assumed, like Varitek, he would be awarded home. So he stopped between 3rd and home.
Big mistake!
In Bill Welke's opinion, Tejada would NOT have likely scored even if the obstruction had NOT occurred. So, when Tejada was tagged out ... he was OUT!
Notice how in the first instance the obstructed runner was awarded the NEXT base even though that is NOT the base the runner would have achieved had he not been obstructed. But that is the requirement of a Type A obstruction award. The umpire MUST award, at a minimum, the NEXT base.
The second instance featured Type B obstruction which does NOT require the umpire to award the next base. The umpire keeps the ball live and "awards" the runner whatever base he (the umpire) thinks the runner would have attained had the obstruction not occurred. In the Tejada's case, that was 3rd. So, when Tejada advanced beyond the base to which he was protected, he did so at his own risk.
Two completely different types of obstruction - IN ONE GAME!
