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From poking around, it looks like Leyland was cool with burning the DH if he had too, but it looks like he never did.
They did have a utility guy on the roster ready to play C if needed, but you're right -- VMart was the only other true C and also the primary DH.
But! For the playoffs, they kept Santos as the third catcher. Didn't want to get exposed at crunch time.
Interesting.