base mechanics

[Manny A]

I've always treated it this way: If the BU is "stuck" behind second in position to make a call because there's an imminent play there, then he/she is going to have to play catch-up when the runner slows down or stops at second and then continues on. That, to me, is when the PU should call off the BU for any subsequent play at third.

But if there is no play at second base and the runner simply rounds the bag and continues on to third, the BU should have no trouble moving to third to take the play there. That typically happens when the ball is rattling around near the backstop or dugout, and the PU will likely be pinned back there watching to make sure it doesn't enter DBT.