If Castro moves any deeper, the umpire will stop giving the borderline calls, on the grounds that he can not see. The importance of Castro lies almost entirely in the rules, namely how guys without minor-league options can not be treated the same way as those who do still have them. Had we dispensed with Castro earlier in 2019, we'd be feeling uncomfortable now, with Astudillo dinged up. Had Astudillo been optioned (the other main alternative if that spot on the roster was needed), and then got dinged up at Rochester, we still have two MLB-caliber catchers - and if one of the other two catchers was dinged instead, likewise with a quick call-up. It boils down to not doing the irreversible roster move until you have to.