I'm very happy that the casual fan is being introduced to and embracing more advanced concepts (ie: sabermetrics) in baseball understanding/evaluation. Being too simplistic in analysis usually leads to inaccuracies and building a false narrative that can be debunked through empirical evidence.
I say that because Johnny Cueto gave up four runs yesterday and Twitter (yes...I know) was all abuzz about using BABIP as an explanation for his struggles in Kansas City.
Basically, Cueto is getting BABIP'd to death https://t.co/8zY8YQb3DO— Slow Runner (@kevinmaltzy15) October 9, 2015
Regression to the mean? BABIP against Cueto has always been confoundingly low. https://t.co/i90qcgOuSb— Johny Barnett (@JohnyBarnett) October 9, 2015
Johnny Cueto and BABIP continue their falling out.— Andrew Gould (@AndrewGould4) October 9, 2015
So yeah, I mean it's no doubt that Cueto has had a higher BABIP in his time in Kansas City. We have cold/warm/hot hard evidence showing this. Here, let me provide it to you in an excel table:
Definitely Cueto has been unlucky in his tenure as a Royals pitcher. His career BABIP is .276, almost 70 basis points lower. That's a pretty big shift and we should expect that to come down closer to not just his career average but league average too (~.300).
Cueto's ERA as a Royal (as of this writing) is 4.76. His ERA with the Reds in 2015 was 2.62. That's of course a huge difference of more than two runs per nine. We didn't necessarily expect his ERA to maintain around 2.62 when he came to Kansas City, but ERA is a function of team defense and the Royals defense is quite good. Some regression was in order likely, but not 2+ runs per nine.
So I agree that BABIP is a reason for Cueto's poor ERA/performance so far as a Royal, but it isn't the SOLE reason.
One thing that's kinda gotten lost in the BABIP/ERA narrative is Cueto's declining strikeout rate and in turn his increased FIP. Here's another excel chart:
It's not as a dramatic increase as his ERA/BABIP, but it's an increase of slightly less than a full run over nine. In Cincy he was a top-20 pitcher in baseball. For the Royals he's been more like Aaron Harang.
And this makes sense too. Cueto is striking out two fewer batters per nine with the Royals. This means that more balls are going to be put in play, and with a high BABIP like he has then more are going to fall when they do go into play.
There's an argument perhaps that Cueto's FIP is affecting his ERA perhaps. It's over simplistic to say, but Cueto needs to strike out more hitters in the few remaining game(s) he potentially has left with the Royals. We can't blame Cueto really for his high BABIP (something he has no control over in theory), but we can blame him for striking out less (something he has full control over in theory). If his strikeout rate regressed then he'd possibly have a better ERA.
Now, why is he striking out drastically less batters? That's an entirely different article.