Mechanics

[varefump]

I agree with debeau.
On a possible pulled foot from the 'C' position, I check with my plate umpire to see if he/she has a 'foot'.
What if you, as the base umpire, call the out at first for the 3rd out of the inning, which causes all runners to stop their advancement.
After which you go to your partner and he/she now has a pulled foot. Now you have to put runners back on the bases and explain to the offensive coach that his runner from third didn't score on the because she failed to continue on after the third out call.
I've always found it better to get the play right the first time. In this situation, it is the base umpire's call on 'safe or out', but if he needs help to make that call, get it first before making any guess on the play.
If the plate umpire can't glance at first base at the moment of the catch, then he's not working hard enough.
But by all means, talk about this play in your pre-game.