[BretMan]

I had found the passage quoted by Cecil above and was just about to post it here. He beat me to it, so I'll move on to my next piece of evidence...

ASA Umpire Manual (2008 ed.), page 201: Collision:

"Simply because there is contact between the defensive and offensive player does not mean that obstruction or interference has occured. This is definitely NOT (emphasis, their's) the case.

The field is layed out in such a manner that it puts the offensive and defensive player on a collision course.

The right-handed batter, for example, who lays down a bunt in front of home plate is on a collision course with the catcher while running in a direct line to first base. Each player at this point is within legal rights- the batter taking a direct line to first base and the catcher coming out from behind home plate to field the ball.

The questions that must be answered are:

1. Did the batter alter their (sic) direction in any way drawing contact, in an attempt to receive an obstruction call?

2. Did the catcher alter the attempt to field the ball in any way so as to draw the interference?

3. Could the catcher actually make a play?"

My third piece of evidence- at the risk of being blasted for using a baseball reference- was going to be the infamous "no call" by umpire Larry Barnett in the 1975 World Series, on a bunt play involving Red's batter Eddie Armbrister and Red Sox catcher Carton Fisk. Okay...different sport, but same play and same concept (if you're not familiar with the play, Google it).

As long as both players, the batter and the catcher, are making an immediate and direct move to do what they're "supposed to be doing", contact may be ruled as incidental- no penalty, play on.

If one hesitates, pauses, alters their path or in some way purposely initiates the contact, the umpire has to judge it a little differently and interference or obstruction can be the call. The close proximity of the batter and catcher on this play, and the inevitable crossing of their paths, has led to an interpretation and ruling that acknowledges the unique circumstances.