HBP scenario - FED
 

Hypothetical situation that almost happened to me a few weeks ago.
I'm at "C" position. Right handed batter. Pitch is above and behind batter. Batter tries to duck under pitch. I clearly see ball graze the batters back then contact his bat. U1 only sees and (or hears) contact with bat and calls "Foul Ball".

Exactly what should I do and when?

I admit this is the wimpy way out, but ...

If offense is not putting up a fuss, then I am just making eye contact with PU to let him know I have something and see if he wants to talk.

If offense is putting up a fuss, I'm going in to see if he wants to talk.

Nothing unless he asks.

As a BU, how would you have handled the same situation with the exception that the ball went into fair territory after contacting the bat? Having "clearly" seen the ball contact the batter would you allow the play to continue even if the plate umpire is pointing toward fair territory? Regardless of whether the ball hit the player then bat or bat then player, the ball contacting the batter creates a dead ball. If there is any debate beyond that, you can have that discussion after calling a dead ball because nothing will change the fact that the ball was dead when it hit the player.

Bringing this back to the OP, I think you can probably answer the question based on how you would handle my example. I say that because this is a situation I bring up with my partner in pregame (albeit we usually discuss it with regard to a normal swing that hits the batter). My preference and what I request of my partner is that he/she kill it if they are sure the ball has hit the player. After that give me a sign if it is complicated enough to need discussion. Conversely, I've had some partners tell me to leave it alone when I'm on the bases and that is what I do. To me realizing you can't see everything from behind the plate and having a plan on how to deal with it is the key.

Pregame usually goes as follows: "if you see a batted ball off the player in the box and I don't call it, call it for me." This is not the same situation. In this situation, as PU I would expect you to keep it to yourself unless I ask, which I will do if the offense is complaining about it. if you are sure it hit the batter first, I will change it from foul ball to batter take your base and then deal with the defensive coach if he wants to argue.

Pitched ball off the batter (possibly), I'm doing nothing. This belongs, 100%, to the plate umpire.

I'm always there if the PU asks me about it. If not, see paragraph #1.

Batted ball hitting BR while they are still in the box, I want BU calling this immediately. Pitched ball? No. PU's call. If PU is given reason to ask for help (or has reason to ask on his own), BU should tell him what he saw and PU should then stick with his call or change it.