I've always been a huge believer in how much a catcher influences a pitcher's success or not. The old CERA arguments got out of hand as many used the numbers inappropriately. CERA should not be used to compare catcher across the league or from different teams and different years.
That being said, here are the Sox CERA numbers: (Note: some small sample sizes here due to the personal caddy nature of our catcher usage.)
CERA (IP)
Leon vs Vaz
2.19 (156)/ 13.50 (5.1) with Sale
[Note: 3.02 w Flowers (552), 2.51 w AJP (226), 3.53 Avila (112)]P
4.59(139)/ 7.11 (6.1) with Porcello
[Career: 4.09 (273) Leon, 4.55 (113 Swihart), 3.86 (100) Vaz, 4.17 Avila (578), 4.32 (296) Laird, 5.38 (82) Holaday]
13.50 (4)/ 3.01 (117) with Pomeranz
[Career: 3.01 (117) Vaz, 7.12 Leon (24), 3.32 (41) Holaday, 1.99 (131) Norris, 5.73 (71) Rosario]
4.55 (87)/ 4.55 (87), Hanigan 3.78 (50), 4.08 (71) Swihart w ERod (career only)
3.23 (109)/ 4.30 (163) w Price career only
[2.85 (473) Molina, 3.06 (191) Jaso, 3.61 (162) Shoppach, 3.09 (128) Navarro]
1.74 (21)/ 4.32 (33) w Barnes
[Career: 4.32 (60) Leon, 3.30 (60) Vaz, 4.50 (30) Swihart, 5.93 (27) Swi]
2.16 (25)/ 4.38 (25) w Hembree
[Career: 3.69 (46) Leon, 3.71 (51) Vaz, 1.83 (20) Hanigan, 1.20 (15) Swi]
1.64 (22)/ 1.35 (27) w Kimbrel
[Career: 2.38 (42) Leon, 1.62 (44) Vaz, 1.82 (158) McCann, 2.06 (48) Gattis, 2.01 (45) Norris, 0.00 (41) D Ross!!!]
Career Only:
Kelly
2.67 (27) Leon, 2.62 (55) Vaz, 2.81 (176) Molina, 4.83 (91) Hanigan, 4.44 (77) T Cruz, 5.10 (60) Swihart, 3.94 (32) D Ross
Abad
6.23 Leon (17), 2.59 (24) Vaz, 4.22 (43) Castro, 2.75 (36) Suzuki, 2.06 (35) Norris, 3.03 (30) Vogt