OBS or Tag Up

[Big Slick]

I'm confused as to why this is a difficult situation. According to a recent thread about umpire responsibilities with multiple runners, this seems rather routine.

Originally Posted by tcannizzo

2-man mechanics ASA:
R1 on 3B, R2 on 2B, B3 hits long fly ball down the left field line, 175-180ft.
PU has catch/no catch, fair/foul, and R1.
BU comes inside, button hooks for tag up responsibilities for R2.

F7 makes heroic effort, but does not make catch in either case. Fair ball.

Apparently there was OBS at 1B by F3 on B3 and was not seen by either ump due to the angles on the play, which was brought up by each OC.
...

What are the best mechanics on this?

PU Priority one: fair foul. Being that the ball is hit down the left field line, that forces PU to move up the line, most likely past the holding zone. PU's position may even resemble more of a calling position at 3rd, which is good considering . . .

PU Priority two: PU needs to read the play and a) take any runner being played on at home OR b) non BR's at 3rd. In this particular play, the ball was not caught and now PU must take non BR's at third. R1 in this case will score without a play. If one is so worried about R1 missing the plate, PU can peek 45-50 feet. IMO, too many umpire are worried about runners missing the plate without a play.

Now let's turn our attention to BU.
BU Priority one: R2 tag at second. As you stated, BU came inside. That's fine, but now he must line himself up with 2nd and the ball, while realizing that the BR is to his back. Once the ball is not caught (or caught), BU will watch the tag up and hold his position at 2nd being if R2 goes to 3rd, it is not his responsibility. While not stated in the OP, I'm sure R1 was off when the ball isn't caught. Therefore, BU should look ahead and make sure PU is where he is suppose to be (at 3rd) and . .
BU Priority two: BR. BU should now quickly focus on the BR by opening up to 1st and the ball (maybe even getting a bit deeper into the infield to avoid throwing lanes) and read what BR is doing. If she round and goes to 2nd, take a calling position at 2nd. If she stops at 1st, then move to a calling position at first.