What does that even mean? The need for an "emergency catcher" implies that you carry two catchers and both of them go down in the same game. Even if the day's starting catcher goes down on the first pitch of the game and the other is the DH, you're swapping the other catcher behind the plate immediately. Having to mix and match hitting a pitcher in the lineup 3-4 times has way less potential for damage throughout the game than throwing a barely-trained "emergency catcher" behind the plate and hoping that he doesn't colossally **** up somewhere between catching, throwing out runners, communicating with the pitchers while calling the game, etc... Planning around this non-event by spending any kind of organizational resources to "train emergency catchers" is beyond pointless. In the one-in-a-million chance that both catchers go down, any player on the field would be capable of strapping the pads on and slogging through a couple innings behind the plate even without any kind of preparation or notice. There's no advance licensing component required to wear shin guards.