[Andy]

Wade nailed it.

In any C position, it is almost impossible to get a good look at the play described. Even though the PU has the responsibility of the runner coming home and the touch of third base by the trailing runner, s/he also has the responsibility of help at first.

Having the luxury to sit here and contemplate the play, I would say the priority due to the game situation would be the play at first. This play could end or prolong the ball game. I would want to get that one right. I would think that everyone in the park would be focused on that play and if the trail runner missed third, it is highly unlikely that anyone would pick that up.