Swinging Out of the Zone and Really Swinging Out of the Zone

A few years ago — unfortunately I don’t remember where — I remember seeing an article beginning with the premise that not all pitches out of the strike zone are alike. What we offer here on FanGraphs is O-Swing%, a rate of swings at pitches out of the PITCHf/x zone. Yet this groups all such swings and pitches together, and for a hitter, swinging at a pitch an inch outside is different from swinging at a pitch a foot outside. One might indicate a little better discipline than the other. The author decided to see if there were cases where O-Swing% was misleading, given the distribution of swings at balls. What he found was, no, it’s fine. Over full seasons, there’s no need to get more granular. But what about when you’re short of full seasons?

This little study was inspired by Jose Abreu, and a hunch. Abreu, right now, owns a 152 wRC+ in his first-ever exposure to the bigs, and his isolated slugging percentage is an impossible .369. He’s already been everything the White Sox could’ve dreamed of. Abreu also owns one of baseball’s higher O-Swing% rates, at 39%. He’s been fed a lot of pitches out of the zone, and he’s swung at a lot of pitches out of the zone, and that trait and success don’t always go hand in hand. What I wondered was: has Abreu been swinging at borderline balls, or has he really been fishing? He’s already demonstrated that he can drive pitches on any of the edges. His functional zone might just be bigger than the average zone. To what degree has his zone really expanded?

I decided to look at the 225 hitters who, so far this year, have seen at least 250 pitches. On average, they’ve seen more than 360. Our version of O-Swing% uses the PITCHf/x strike zone. I decided to create a box bigger than the PITCHf/x strike zone, to include those more borderline balls, which make for more forgivable swings. Laterally, I set thresholds of a foot from the center of the plate, and vertically, the box stretches from 1.5 feet off the ground to 3.5 feet off the ground. So we have a box, two feet by two feet. Within the box is the strike zone, and some area outside of the strike zone. I was wondering about the pitches outside of this larger box.

If you’re curious, 56% of pitches so far to Pablo Sandoval and Freddie Freeman have been outside of that box. Right behind are Yasiel Puig, Gerardo Parra, and Abreu, at 55%. At the other end, David Wright and Travis d’Arnaud are tied at 36%. Anthony Rendon’s at 37%, Andrelton Simmons is at 38%, and Eric Young, Ruben Tejada, and Dustin Pedroia are at 39%. It would appear, at a glance, the Mets have been seeing a lot of strikes, but that’s a separate investigation.

Shin-Soo Choo and Matt Joyce have swung at just 9% of pitches outside of the larger box. Those are the lowest rates in baseball, with Trevor Plouffe in third at 11%. The highest rate belongs to Mike Zunino, at 47%. This probably isn’t a surprise — Zunino has baseball’s highest overall swing rate, and he’s swung at nearly half of the obvious balls he’s been thrown. No one else is within six percentage points of Zunino, with Jonathan Schoop and Brandon Phillips equal at 41%.

But this is less about an alternative O-Swing%, and more about the difference between this version of O-Swing% and the FanGraphs version of O-Swing%. Let’s look at a couple tables, shall we? First, the ten guys with the greatest positive difference between this O-Swing% and the familiar O-Swing%. That is, these guys have swung at more obvious balls than borderline balls. Keep in mind this is relative to a league average of -3%. This actually measures percentage points, not percent.

Player	Difference
Brandon Moss	4%
Juan Uribe	4%
Yasiel Puig	4%
Mark Trumbo	4%
Andre Ethier	3%
Gerardo Parra	3%
Brad Miller	2%
Erick Aybar	2%
Coco Crisp	2%
Michael Cuddyer	2%

Brandon Moss has a regular O-Swing% of 32%. Yet he’s swung at 36% of pitches outside of the larger box, which seems to be more bad than good. That difference ties Moss with a couple of Dodgers and one injured Diamondback. There’s another Dodger right behind Trumbo. Personally, however, I’m more interested in this second table, capturing the other end of the data:

Player	Difference
Marc Krauss	-10%
Travis Snider	-9%
Brandon Belt	-8%
Alex Gordon	-8%
Nick Swisher	-8%
Alex Avila	-8%
Charlie Blackmon	-7%
Justin Morneau	-7%
Zack Cozart	-7%
Nick Castellanos	-7%

My Abreu hunch is only partially true, meaning it’s hardly true at all — his adjusted O-Swing% is four percentage points lower than his regular O-Swing%. Marc Krauss, though, shows up at ten percentage points lower, suggesting he’s been less willing to chase than his O-Swing% would otherwise indicate. Ditto Travis Snider, and Brandon Belt is interesting because while he’s been unwilling to chase, he’s been very aggressive at obvious down-the-middle strikes. Belt has baseball’s third-highest rate of swings at pitches inside the box, and so it could be that he’s selectively aggressive, instead of just regular aggressive. He does presently own a career-best ISO, which could be a coincidence, or a non-coincidence.

I’m hesitant to make too much of this, in no small part because I don’t know how to make too much of this, but I wonder if this might be a decent indication of “true” O-Swing%. I wonder if the guys in the first table might have their O-Swing% rates regress up, while the guys in the second table have their rates regress down. That’s nothing I can figure out today. And another thing I’ve figured out today is that, no, Jose Abreu hasn’t necessarily been swinging with controlled aggression. He has been willing to chase, particularly down and just above the dirt. It could be that’s going to prove to be Abreu’s downfall. Or it could be Abreu’s too good at converting a lot of his swings into value, and pitchers trying to get him to chase will make mistakes. It’s true that not all pitches out of the zone are created alike, and you might just have to stray pretty far from the zone to consistently get Abreu out.