The meaning of Trevor Cahill

Preparatory to a larger (and future) discussion about how we should talk about Cy Young candidates, Dave Cameron introduces a highly relevant subject:

    One comment that keeps arising, however, is about the correlation between Trevor Cahill‘s BABIP and his sinker, specifically his ground ball rate. Several people assert that Cahill is inducing weak, easy to field contact by pounding his sinker at the bottom of the strike zone, and that’s why his BABIP is just .217. There are a few problems with this assertion, though.

    We know that BABIP on groundballs is higher than on flyballs, as a ball is more likely to sneak between two infielders than it is to fall in front of an outfielder. In general, groundball pitchers will post higher than average BABIPs, not the other way around, though the effect is generally pretty small.

    The other problem… well, we’ll just demonstrate it this way.

    Trevor Cahill: 56% GB%, 14.9% LD%, 29.1% FB%, .217 BABIP

    Justin Masterson: 62.3% GB%, 14.9% LD%, 22.8% FB%, .344 BABIP

This might be my last post today, because I don't want anyone to miss it. And I don't want anyone to miss it, because -- and I'm sorry to speak so frankly here -- I'm getting just a little tired of having to revisit this ground, again and again and again.

Lately, every week in my Tuesday chat, at least one person asks me about some pitcher with a low ERA and a lower BABiP. As gently as I can, I explain that a .217 (or a .223, or a .235, or a whatever) BABiP simply isn't sustainable. Not for Trevor Cahill or Tim Hudson or Cy Young or Greg Maddux or anyone else. Next, the questions queue gets loaded with arguments from the same guy, and usually other guys too, that while such a BABiP might not be sustainable for most pitchers, it's sustainable for this pitcher because of X or Y or Z. These arguments -- most of which I don't post -- only become more pleading or strident as the hour moves along.

It's not sustainable, and it doesn't matter who's doing the pitching. Trevor Cahill is an incredibly talented young man. I would trade my left arm for his right arm (well, most of my left arm; I need some of it to do the Jim Abbott thing). But if can consistently keep his BABiP below .250 -- let alone .220 he'll be the first since the 1970s.

There's still a discussion about BABiP to be had, around the margins.

But .217, really? You're smarter than that.