O-Swing% Correlations
As David announced earlier this week, fangraphs now has swing data for hitters, giving us a breakdown of who swings at what and how often. This is just another great resource he’s added to the stat pages. And, as always, more data means a chance for more research.
One of the first things I wanted to look at in this data was the effects of swinging at pitches outside of the strike zone. It’s been a sabermetric credo for a while now that good hitters are selective at the plate and don’t chase pitches out of the zone, but players like Vladimir Guerrero, Nomar Garciaparra, Ivan Rodriguez, and Ichiro Suzuki have all had tremendous careers despite swinging at pitches that no sane person would think they could hit. If you can be a hall of fame hitter without being selective, how important is it?
So, I decided to take the list of qualified hitters for 2008 (197 in all) and look at the correlations between their O-Swing%, which measures how often they swing at pitches out of the strike zone, and their BB% and K% rates. Intuitively, I would have thought that the more often a player swings at pitches that would otherwise be called balls, he’d have a lower walk rate and a higher strikeout rate. Here are the results:
O-Swing%/BB% correlation: -0.67
O-Swing%/K% correlation: -0.10
The walk rate correlation matches up with expectations, as there’s a strong negative correlation between swinging at pitches outside the strike zone and walk rate. This, of course, makes sense – the more often you swing at pitches that would have otherwise been called balls, the less likely you are to draw four balls in any given plate appearance. Guys like Matt Diaz eschew the walk through sheer determination.
However, look at the correlation between O-Swing% and K%. I’d have expected a fairly strong positive correlation, as you tend to think of guys flailing at sliders in the dirt as more prone to strikeouts. However, the correlation barely exists at all, and it goes to the negative to the point that there is any correlation. We see this manifest in guys like Erick Aybar and A.J. Pierzynski, who both swing at 37% of pitches outside of the strike zone but strikeout just 7% and 6% respectively.
It appears that players who swing at pitches outside of the zone do so because they can hit them – it is the ability to make contact that creates the aggressive approach, and not just a player’s desire to hack at anything.
Dave is the Managing Editor of FanGraphs.
I’m wondering if data on BABIP splits for O-Contact and Z-Contact are available?
Thanks for all the great analysis.
Hmm…. it’s possible to add them, but we’ll see. I don’t see them getting added in the immediate future, but if there’s really enough demand for them, it could get pushed to the top of the to-do list.
Dave: What’s fun is you can combine O-Swing% and Zone% to get an even higher correlation with BB%. I’ve always thought it’d be fun to have “expected Walks” and see if batters are above/blow and see how that fluctuates from year to year.
Well, from watching Ichiro over the years it appears that much of the time when he is swinging at balls out of the zone he’s doing it precisely to avoid striking out. Sometimes when he gets into a 2 strike count against certain pitchers he goes into this “protect the plate” mode where he’ll swing at just about anything with no intent other than fouling it off. Certain pitchers seem to be realize this and exploit it by just throwing garbage, but sometimes they leave it up or Ichiro manages to golf one off his shoetops. I’ve seen this in Vlad too, but he seems to be a little less systematic about it (swinging at stuff way out of the zone on any count, and frequently making contact anyway).
I would assume that O-Swing% would correlate pretty strongly with overall swing% and therefore also called strike%, which would account for the result pretty intuitively. To strike out players of this sort, pitchers are less able to rely on called strikes, and it’s difficult to get 3 or even 2 swinging strikes in an AB.
Isn’t there a positive correlation between walk % and k %?
It seems to me that players who swing at a lot of pitches (like Ichiro) would get deep into counts a lot less than players who hardly swing at all (like Cust). The deeper into counts you get, the more likely you are to walk AND strike out.
Rich, when I first saw these plate discipline stats, I also thought that it would be nice to see the BABIP splits for them. Everyone loves to talk about how Vladimir Guerrero can get the bat on anything within 5 feet of the plate, but is he turning these pitches into hits? Is it really worth it for him to swing at them?
Walks come from not swinging. Strikeouts come from not knowing the strike zone. What I’ve found is that the freest swingers (and the most conservative swingers) are the ones who have the best strike zone judgment. To be that extreme (cough*Vlad Guererro*cough), you need to be good at what you’re doing.
Where does Matt Diaz fit into that spectrum?
I think I understand why O% is not strongly correlated with K%. Let’s say a pitcher is facing a guy who is swinging at a lot of pitches outside of the strike zone. How do you think this pitcher would approach this player? He’d probably throw a lot of pitches outside of the zone. Vice versa seems true also, the less someone swings outside of the zone, the more strikes they will throw or attempt to throw.
I think they key to walks is an ideal mix of swinging and not swinging. You want to swing at pitches only inside the strike zone but if you dont swing at all your gonna get more strikes.
I wonder if umpire consistency correlates too. If an ump has a zone that’s wide, then it makes sense to swing at more strikes outside the zone.
Kinda unrelated but it made me think of maybe if there’s a study between umps with big zones and O-swing%, I’m assuming there is.