He's so under-rated, it is pathetic. Also, Vaz cannot catch every game. If he did, his offense would suffer.
Vaz is having a great year, offensively, but he'd have to hit .500 to make up for this:
Sale:
w Leon 3.49 (.608 OPSAgainst)
w Vaz 6.68 (.956)
Career: 2.67 (.573) w Leon and 4.61 (.763) w Vaz
Porcello
w Leon 4.12 (.703)
w Vaz 7.41 (.933)
Career: 4.13 (.728) w Leon and 4.87 (.784) w Vaz.
It makes total sense to have Vaz catch 3/5 games and maybe a few games with Porcello here and there.
It certainly is not "pathetic" to think starting a catcher that almost halves the ERA with Sale. Porcello might be debatable. Price is doing better with Vaz, this year, despite doing much better with Leon before.