FanPost

The Good, The Bad, And The Ugly (Of Plate Discipline)

In almost every important way, the start of the baseball season is the best time of year. One week you’re trudging through snow and subsisting on split-squad spring training highlights, and the next you’re- well, you’re still trudging through snow this year, but you’re doing it with real baseball happening every day. There will be a lot of baseball happening all year, but this one-month burst of baseball to start the season is always exhilarating. There are downsides, though. With only 75 or so plate appearances a player, we’re in the awkward twilight zone where it’s too early to trust most data, but we’ve watched enough baseball to form opinions that will take all year to shake. You know what I’m talking about- Kolten Wong will never hit a line drive again, Dexter Fowler is washed up, Joey Votto forgot how to hit a baseball.

It’s too early to think of these as anything but small-sample-size theater. There’s one place, though, where we have juuuuust enough sample size to start taking a little meaning. Plate discipline stats stabilize really quickly, and a few Cardinals have made noteworthy changes. Below are three updates on what we can take from the early data.

Tommy Pham Has Elite Plate Discipline Now

I’ll admit, I didn’t see this one coming. Pham literally has bad eyes. His transformation into a high-walk, low-strikeout hitter was already noticeable last year. It’s only accelerated this year. His chase rate (the percentage of out of zone pitches he swings at) has held steady this year at a career-low 20% (20.1% this year, to be exact). Somehow, though, he’s paired this with a career-high in-zone swing rate. It really shouldn’t be possible to swing at more strikes while still laying off just as many balls, but Tommy has accomplished it and maintained a high contact rate to boot. I looked last year at how you can approximate K%-BB% from these plate discipline stats, and put simply, it looks like you can explain the downtick in strikeouts and uptick in walks to his superior plate approach.

Now, in the paragraph above, I said elite. You want some elite comps? I ran some similarity scores of Pham’s numbers so far this year with the full 2017 seasons of every hitter in the majors. I’m not going to bore you with tables of z-scores, but here are five names from his top 10 comps among qualified hitters: Carlos Santana, Buster Posey, Mike Trout, Anthony Rendon, and Christian Yelich. Uh, yeah, that will do. Kris Bryant scored highly as well, though he has a lot more swing-and-miss than his fellow Las Vegas native. If Pham can keep up his normal power on contact and speed, this could be a great year.

Marcell Ozuna Will Walk More

This one isn’t quite as exciting as Pham’s. In Pham’s case, he’s elite already, and the numbers just drive that point home. Ozuna just straight up is not walking this year. His plate discipline numbers, however, are right in line with his historical averages. For his career, he’s made this hitting style work to the tune of a 22% K rate and a 7% walk rate, within spitting distance of league average in both numbers. To the extent that there’s something to be concerned about with Ozuna, it is that he’s not hitting for power, but a quick and non-scientific look at Baseball Savant shows that he has barreled six balls and only gotten two hits to show for it, a ratio that certainly won’t continue:



Matt Carpenter Is Having Issues

In last year’s article, I made a quick estimator for K%-BB% using some plate discipline stats. Plugging that formula into 2018 numbers and applying some low PA minimums, Cardinals dominate the bad side of the list. Yairo Munoz couldn’t hit a thing in his brief 20-PA major league stint. Paul DeJong is a professional misser of baseballs. Matt Carpenter-- wait, Matt Carpenter?? He has the 11th-highest estimate, sandwiched right in between noted strikeout enthusiasts Ian Happ and Giancarlo Stanton. Not great, Matt. What’s truly remarkable about this statistic is that everyone else on the list is actually striking out a ton more than they walk. Carpenter’s truly abysmal plate discipline this year has been masked by an unsustainably high amount of walks. Looking at these numbers, it’s almost impossible to believe he isn’t hurt.

Carpenter is swinging at 48% of pitches in the strike zone. To put that in context, Xander Bogaerts was dead last in the majors in Z-Swing% at 53. This isn’t out of all pitches- it’s out of strikes. It’s hard to explain how low that is, because there simply isn’t much precedent for major league hitters swinging this rarely. The last person to swing at less than 50% of strikes was…. 2014 Matt Carpenter. In that year, though, he hit 95% of strikes he swung at, basically making it impossible to throw anything past him. When he does swing this year, it almost doesn’t matter. His zone contact rate is a ghastly 75%. You are not going to like the 2017 comparables. Only Joey Gallo had a worse contact rate on pitches in the zone, and he made up for it with the third-highest ISO in baseball. Put simply, if you’re missing that often, you need to do some real damage when you connect. This isn’t a case of a small sample making Carpenter look bad- his inability to hit strikes is absolutely unprecedented in his career. His previous low for an 18-game stretch was roughly 80%.

I think Carpenter is hurt. I can’t really imagine these numbers declining that sharply otherwise. For the sake of argument, though, let’s construct a player that looks like Matt Carpenter looks if this is the new him. First, I gave him a 12% walk rate and 29% strikeout rate- I reached these numbers by regressing his current plate discipline numbers back towards his career average as per Tom Tango's The Book. Let’s assume he puts the other 59% in play. To handle these, I took advantage of Baseball Savant’s xwOBA stat, which provides an expected wOBA for a given angle and speed of hit. To get a large enough sample, I took the xwOBA of every home run and ball in play that Carpenter recorded from 2016 to the present. The resultant Frankenstein player of Carpenter’s new plate discipline skill and old power on contact skill projects to a .339 wOBA- marginally above a league average hitter but not by much. This, again, is assuming that his contact quality stays as high as it has been over the past 2+ years. Given his vastly decreased contact rate, I think that’s an optimistic assumption.

If the idea of Matt Carpenter’s defense attached to someone who hits like Jedd Gyorko doesn’t frighten you, it should. I’m not even sure that this hypothetical player merits a roster spot. Now, again, I think the most likely explanation is that Carpenter is hurt, and that a little rest and recuperation could get him back up to a more historically normal contact rate. That said, I’m absolutely terrified. We could be witnessing an Allen Craig-like decline right before our eyes. When I think about aging, I think about a graceful decline over years, a player losing a half a win a year until he fades away. It doesn’t always happen that way, though. Sometimes it’s a string of seasons with no drop off, followed by a sudden cliff. I hope this is not the case with Carpenter. For the first time in years, though, I’m worried about his long-term future.

Conclusion

Well, there you have it. One great stat, one encouraging stat, and one terrifying stat. I hasten to point out that even though we’re dealing with numbers that stabilize quickly, they’re not the final say in the matter. Maybe tomorrow Pham’s contacts won’t work. Maybe Ozuna really has become a less patient hitter. Maybe Carpenter has been sleeping on the wrong side of the bed, and he’ll wake up tomorrow as good as he ever was. More data is always better for figuring these things out. That said, I find these stats make me enjoy the games more as I watch. I marvel over Pham and fret over Carpenter in a way that I just couldn’t quite reach without having seen the underlying stats.

Note: All stats current as of games of Saturday, 4/21.