One way to look at it is that every throw back from catcher to pitcher is the same as 1/2 a pitch. If a catcher was on defense for 7 innings at 15 pitches per inning, he now is at the equivalent of about 55. If you have him pitch 1/2 of the next game after 3 or 4 innings of rest, he might have 17 pitch innings due to fatigue or another 50 total. Is he catching the next day again? Wow! Did your starting pitcher in the first game deliver all 105 pitches in that game? No? That's what your asking of the stud catcher/pitcher during the course of the day. Only to do it all again the next day? Ouch!!