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Mike Napoli and the case of the expanding strike zone

It's easy to draw conclusions about why a hitter is struggling. It's harder and less satisfying to shrug and say we don't know, but it's probably correct.

Kim Klement-USA TODAY Sports

There is a narrative developing in the Boston media around the Red Sox season. On reflection, that is a very imprecise statement - there are a lot of narratives, as you might imagine! But I'm not here to write about Hanley Ramirez's supposed laziness, or how Jonny Gomes would know how to make this team win, because those are the last things in the world I would ever want to write about. What I'm referring to is the growing strike zone.

To people plugged into the sabermetric world, it's both validating and laughable when broadcasters or reporters talk about their sense that the strike zone is larger. On the one hand, nice! This is something that has been shown quantitatively multiple times, so it's nice to see it entering the mainstream consciousness. On the other hand, this isn't new knowledge; stop acting like you've made a groundbreaking discovery. I've had a lot of time to think about this, because I listen a lot of Red Sox broadcasts, and pretty much every time Mike Napoli strikes out looking, the topic is broached.

Napoli has been vocal about his (true) sense that the strike zone is larger, particularly at or below the knees, and it's an easy thing to point to as a culprit for the struggling Red Sox offense. So much so that John Henry, principal owner of the Red Sox, went so far as to suggest that players needed to adjust to this new reality, abandon the patient approach that is Boston's hallmark, and start swinging at more first pitches.

It's difficult to look at easily-accessible data and attempt to suss this out, because batters and pitches don't make these decisions in a vacuum. If the strike zone is larger, you might expect to see more strikes, but it's totally possible that, for example, pitchers will continue to throw to the edges of the zone, with the same mix of balls and strikes, but all further from the center and harder to hit as a result. That said, I want to try, focusing somewhat on Napoli as a case study.

Using the wonderful Baseball Savant, I took every hitter who has seen at least 500 pitches, and looked at the number of pitches they had seen in each count. The top of the first-pitch strike leaderboard has a lot of the names you would expect: free-swingers, slap-hitters, and those with a little of both, like Tyler Flowers (67.5 percent), Michael Morse (66.9 percent), or Billy Hamilton (63.1 percent). There are some incongruous names, like Ryan Braun, who has a swing rate in line with his career norms and a walk rate about a point and a half higher, but for the most part, it's unsurprising.

Mike Napoli is not near the top, nor is he in the middle. He is 226th of 257, at 49.5 percent. He is one of 34 hitters in the sample that see more first-pitch balls than strikes. Maybe this is different than the previous year, but again, I think it would be misleading to present the percentages side-by-side and act as if differences are clearly reflective of a different strike zone. It's interesting to see that pitchers are not particularly aggressive when pitching to Napoli, whether that is more or less true than in 2014.

He is notably high when looking at the percent of pitches coming in two-strike counts, 38th, at 31.3 percent. But I would argue this is more a function of his patient approach than any aggressiveness on the part of opposing pitchers; Napoli is even higher on the 3-ball leaderboard, in 29th at 10.5 percent. I don't really know what to make of this; again, the constant adjustments that are an inherent part of the batter-pitcher matchup make comparing counts from one year to another really difficult. Mike Napoli has an 84 wRC+, and -0.1 WAR, but he also has a 25.8 percent strikeout rate (career average 26.6 percent), a 12.0 percent walk rate (career average 12.5 percent), and a .176 ISO (career average .231).

Two years ago, he had almost 4 WAR with a 32.4 percent strikeout rate; last year, he had between 2 and 3 WAR with a .171 ISO. His power is definitely lower than expected, but power is the sort of thing that fluctuates a lot. In my opinion, the most likely culprit is randomness, which is super boring and not very fun to read about, so, sorry! I think he's probably going to be pretty good going forward, because Mike Napoli has been pretty good at baseball in the recent past. Baseball analysis is hard.

Again, I don't know what I'm saying. It's really, really difficult to look at relatively simple data and conclude whether or not the expanding strike zone has changed what makes an offense successful. In a last-ditch attempt, I looked at the relationship between team swing rate and wRC+, for 2014 and 2015.

Basically no relationship! If anything, patience is more highly correlated with batting success in 2015. I don't know what that means. Probably nothing. The total rate of pitches thrown in the strike zone in 2014: 44.9 percent. In 2015: 46.0 percent. Make of that what you will.

The strike zone is definitely getting bigger. That is not in doubt. Whether that results in changes in approach is much, much harder to determine, and I didn't come anywhere close. I don't think a slightly larger strike zone has turned Mike Napoli into a sub-replacement player. Baseball is still basically baseball. For a really smart community, I think we do a very bad job of acknowledging and embracing randomness as the frequent reason behind changes in performance. I tried to do so in this article, and I think the result is not very satisfying, so there are perhaps good reasons why. That said, I think stating what we don't know is better than pretending we know everything.

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Henry Druschel is a Contributor at Beyond the Box Score, though it's not entirely clear what of. You can follow him on Twitter at @henrydruschel.