1: As we've discussed a bit here, the M's behavior seems to suggest that they believe catchers impact RA much more than the minimal amount analysts would ascribe to CS, PB, errors, etc. Why would you utilize the immortal platoon of Rob Johnson and Jamie Burke unless you believed catchers had an inordinate impact on RA?
2: cERA and other attempts to measure this effect have always foundered on two issues: sample size and selection bias. The first because, duh and the second because a catcher who only catches Felix is going to look a lot better than a catcher who catches a large number of Carlos Silva starts.
3: Felix is having one of his best seasons ever, and yet he's still had some downright awful games. The crappy game at home vs. LAA comes to mind - a start so bad, Wakamatsu 'called him out' in the press. Baker seems to credit that move with helping Felix to 'focus' better, and notes his results since being trashed by his manager: 3-0, 0.72 ERA in 5 starts. Of course, most M's fans would remember that Johjima caught that Angels game, and hasn't caught him since. Indeed, you can pretty much eyeball Felix's game log and pick out the Johjima starts just be looking to see when Felix gave up runs/XBH. And yes, the sample size in 2009 is laughably small.
So, I took a look at Felix's career splits by catcher. What we get is this:
1958 PAs, 406 Ks, 154 BBs, 52 HRs, 486 H. BABIP: .327
*With everyone else:*
1245 PAs, 277 Ks, 91 BBs, 19 HRs, 263 H. BABIP: .291
If you normalize the BABIP to Felix's career average of .313, you get slash lines of:
*.274/.334/.419 with Johjima*
and *.250/.312/.329 with everyone else.*
In rate terms, that works out to:
H: 23.85% (Johjima, normalized), 22.65% (Field, normalized)
BB: 7.87%, 7.31%
K: 20.74%, 22.25%
HR: 2.66%, 1.53% (whoa)
'The Field' produces a shinier K/BB ratio, but it's not huge. The difference here is almost entirely down to HR rate. It's enough to produce a FIP of ~4 for Johjima and ~3.2 for everyone else. That's big. We keep waiting for 'King Felix' to stop pitching stupid, or for his results to show up and.... they basically have, from 2005-2009, so long as Johjima isn't catching.
But wait! Pizza Cutter's good work on when sample sizes 'stabilize' suggests that HR/FB or HR/PA is really, really volatile. It's true - at 750 PAs, Pizza found HR/PA's r value was only at 0.323. Not nothing, but not near the 0.7 he used as his standard for reliability. So is Johjima the victim of really, really terrible luck on HR/FB? Note that the samples for Felix/Johjima/the field are much, much larger than the 750 PA sample Pizza used (he was trying to use around 1 season of data; we've got more than that).
I have no idea. I'm posting this because I was supposed to go to a meeting and it got cancelled. I just dumped Felix's career splits into excel and estimated IP (and an error in IP will affect FIP, and my est. IP is too low, so knock a bit off the FIP). I suspect it's one of those things where everyone will see their preconceived hypothesis 'vindicated' - if you hate the idea that catchers impact a pitcher's FIP, you can point to the pathetic r value and chalk it up to a fluke. If you love the idea of catcher 'leadership' or 'grit' or 'studying the opposing hitters' or whatever the causal model is actually supposed to be here, you've got a big difference in FIP with no selection bias and so-so samples.
For fun, let's regress these rates and see where we get. If you double the PAs, and use league-average HR/PA figures for the second 'sample', you'll come out with rates of: 2.45% for Johjima and 1.89% for the 'field.' That greatly reduces the FIP gap, but it's still there (as is the HR/PA gap).
So what the hell is this? WHY would Johjima 'create' more HRs? What could he possibly be doing that would create a large effect on HR/PA? It can't really be pitch calling, as Felix was shaking him off repeatedly in the infamous Angels start, only to have the pitches HE wanted to throw get crushed. I'd love to see if there's a difference in GB% by catcher, or in the frequency of off-speed pitches thrown. Felix certainly threw a ton of FBs against the angels, but again, that's not necessarily what Johjima called.