Between 3B & Home

[scyguy]

If BU has trailing runners, PU must take runner into 3B on run-down. As BU I have a BR that is rounding first trying for second. If a throw is into 2B, I better be in position to make a call. What if BR got into a run-down between 2B and 1B and I was trying to take the 3B side of the rundown between 3B and home? Who would make that call? As you can see, my responsibility as BU is the BR.