During a 162 game season no problem carrying 3 Catchers, Manager should be evaluating the whole season anyway, not just counting injuries. In Play-offs it will be about Match-ups, and versatility for the Manager. The more positions you can play, the better to make in game adjustments. 2 Catchers that only play 1 position, holds back a Manager, from moving around other positions. 2 guys basically does the same thing as 1 do. No need. 2 Catchers where one plays 4 or 5 positions, plus switch hits, gives a Manager tons of flexibility.
With Devers, its all about his fielding, he improves here he makes it. Smart Managers knows the importance of good Defense in the Play-offs. You cannot give good teams extra outs, you saw that yesterday.