True, but there are a few pitchers with stark differentials, especially with Swihart and his small sample sizes.
Sale
2.42 w Leon (319)
3.40 w Vaz (53 IP)
O IP with Swihart (very telling.)
(3.02 with Flowers in 552 IP/ 2.51 w AJP in 226/ 3.53 w Avila in 112)
Price
2.83 w Leon (194 IP)
4.32 w Vaz (263)
5.72 w Swihart (11)
(2.85 w Molina 473/3.06 w Jaso 191)
Porcello
4.14 w Leon in 483
4.15 w Vaz in 134
4.59 w Swihart in 118
(4.17 w Avila in 578/ 4.32 w Laird in 296)
ERod is about even
4.00 w Leon in 99
4.08 w Swihart in 71
4.24 w Vaz in 276
Eovalid's sample sizes are small, but he did better with Vaz.
If you look at just Sale and Price, one could argue keeping Leon is the right choice, and trading Vaz could work, if the new guy (like Cervelli) can work with Porcello, Eovaldi and ERod. Since ERod doesn't seem to be affected by who catches him, and Eovaldi is kind of new anyways, and Porcello might be gone after next year, maybe trading Vaz and getting a better hitting catcher makes more sense than I first thought.