There are around 4 umps who have strike zones that are known to not align with the one we think of (like I said somewhere else - it's a tenure track job). The rest might have off nights but on the whole maybe miss one or two calls out of ~75 in a game. That's incredible. I get testy about umpiring, because I umpired for a while at a local level -- teenagers for chrissakes -- and it was the hardest (most skill-needed) job I've ever had or probably ever will have. And I was treated like shit at least once a day. Which is fine, comes with the territory -- but the money does not come with the territory until you become one of the 100 major league umpires. So 99% of all professional umps are doing it essentially because they love the game. Read this. EDIT: I think Hernandez flipped on instant replay because he was vocally opposed in the past but according to a broadcast I caught the other day he has supported its execution this year.