In yesterday's Electric Meter, I set out to find the root of Charlie Morton's struggles over the last month. As it turned out, though, there wasn't much to see. Morton's pitches look the same, his peripherals look better, and the only thing that's different over the last month is the opponent's batting average on balls in play, which is something that's generally hard for a pitcher to control. I concluded with a guess that maybe the slew of lefties that Morton's faced of late (he's generally seeing in the ballpark of five or six lefties every night in the last month) is affecting his BABIP, because that's the only variable that I didn't really account for yesterday. So let's try to account for it.
On the season, righties are hitting just .264 against Morton on balls in play, but lefties are hitting a ridiculous .403. Is this Morton specific, or is this a trend? Let's look at the rest of the staff:
- Jeff Karstens: .211 BABIP vs. righties, .286 BABIP vs. lefties
- Paul Maholm: .233 BABIP vs. righties, .333 BABIP vs. lefties
- Kevin Correia: .274 BABIP vs. righties, .278 BABIP vs. lefties
- James McDonald: .310 BABIP vs. righties, .325 BABIP vs. lefties
Every pitcher in the starting rotation has a lower BABIP vs. righties than they do vs. lefties, though in the cases of Correia and McDonald, it's pretty negligible. McDonald is really the only pitcher on the staff that's a pronounced flyball pitcher, though, so his results don't necessarily compare to groundballers like Morton and Maholm. Correia and Karstens have about the same flyball rate (37.1% and 28.3% respectively), but it's worth noting that the reason for Karstens' big split isn't because lefties have an exceptionally high BABIP against him (league average is usually between .290 and .300), it's because righties have an extremely low number.
It's definitely a small sample size, but for three starters, the defense is much better at turning balls in play into outs for right-handed batters than they are for lefties and two of those starters are the club's two best groundball pitchers. The same thing holds true if we widen the lens a bit; righties have a BABIP of .264 against the entire team, while lefties are at .319.
So why is this happening? The easiest explanation may be that the defense on the left side of the field is just better than the defense on the right side. We're dealing in small sample sizes here, but Ronny Cedeno's UZR at short this year is +3.3 while Neil Walker's at second is -3.9. At first, Lyle Overbay is great at scooping the ball and that surely helps the defense all around, but his UZR this year is a terrible -7.7, which is probably an indication that his range is slipping. That's much worse than the combination of Pedro Alvarez, Brandon Wood, and Josh Harrison at third, which comes out as slightly positive. In the outfield, things are generally stronger, which is possibly why the split doesn't affect James McDonald or Kevin Correia quite as much; Andrew McCutchen has been awesome this year and Jose Tabata, Garrett Jones, and, yes, Matt Diaz all have positive UZRs.
Again, we're dealing with pretty small individual sample sizes this year on the defense, but it's definitely a believable conclusion that Cedeno and Wood/d'Arnaud/Harrison/Alvarez and stronger defensively than Walker and Overbay. It's also possible the defense is shifting for lefties, as I guess yesterday. This is anecdotal, but it seems like there have been more than a few tweeners between Wood and Cedeno that have gone for hits against Morton in the last month or so. I think there's something here, though, even if it's not easy to parse out exactly what it is.