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Paul DeJong Never Stops Improving

The young Cardinals shortstop is making a habit of fixing his flaws

Scott Kane-USA TODAY Sports

Let’s start out with a cheesy platitude. It’s been a great few weeks to be a Cardinals fan. There are almost too many good storylines to keep up with. Mike Matheny is gone. Every rookie pitcher is great. The offense woke up, and Matt Carpenter did something with salsa. The Cards are tied for the second Wild Card spot and within spitting distance of the Cubs. Harrison Bader decided to stop letting fly balls land. Things are looking up in St. Louis. There’s a wonderful trend going on under the hood, though. Far from the flashy catches and gaudy record, Paul DeJong is quietly stepping up. I’d forgive you for not noticing it, because it hasn’t been a dramatic transformation. It hasn’t been leaps and bounds and home runs- or, at least, it hasn’t all been home runs. Under the hood, though, things are getting pretty exciting. Let’s dive deeper.

You know the general deal you’re getting with DeJong. That script was written last year. You’re going to get some dingers. You’re going to get league-average defense at shortstop. Those are lovely. You’ll also get some plate discipline that would make Joey Gallo nod his head knowingly. Or, at least, that used to be the deal. For opposing teams, however, the deal has been getting worse all the time. The power waned briefly when DeJong returned from a broken pinkie finger, but he seems to be getting healthier as he puts the break further in the past, with a .224 ISO over the last twenty games. The defense is as steady as ever. UZR and DRS, the two main publicly available advanced defensive metrics, both have him solidly above average this year. Want something a little less fancy and nebulous than advanced defensive stats? So far this year, he’s converted 82.5% of the balls hit to his zone into outs. If he’d played enough innings to qualify, that would be third among all shortstops, just behind Addison Russell. The defense is good, is the point. I guess we’re here to talk about the plate discipline, then, so let’s do it.

Let’s start with a few definitions. When I say plate discipline, I’m talking about two main things. First, how good is a player at identifying balls and strikes? That’s pretty straightforward- swinging at pitches outside of the strike zone is definitely bad. It’s not quite as clear whether swinging at pitches in the strike zone is good; not all pitches in the zone are created equal, after all. Still, if you want a first pass at it, swinging at strikes is probably good. Now, despite his high-strikeout ways last year, I never considered DeJong undisciplined at the plate. Aside from a rather swing-happy approach, he was pretty average in which pitches he chose to swing at. As the year went on, he also swung less and less often, at both strikes and balls:

You could probably use some context for these graphs. They’re just lines hanging in space, with no real concept of what’s good or bad. Well, league average O-Swing% was 30 last year and is 30.7 this year. League average Z-Swing% was 66.7 last year and is 67.3 this year. They tend to be pretty consistent. What that means, writ large, is that DeJong mostly had an average eye for balls and strikes last year. Maybe he was a little aggressive early in the year, but he was equally aggressive on balls and strikes- just a matter of approach, not really of recognition. Well, he had an offseason to think about how to approach an at-bat. Let’s see what his swing rates look like now:

Honestly, it doesn’t look like there’s much here at first glance. Aside from a brief period of swinging at almost nothing out of the zone, DeJong has made one main change from last year: he’s swinging meaningfully less often. He’s swinging at pitches about 7% of the time less than last year. In my inexpert opinion, that seems like a valuable change to make, as someone with his power is going to draw a lot of pitches out of the zone, so a more patient approach overall is likely to get some free walks as well as cut down on swings at pitches he can’t do much with. So far, so good. Let’s move on to the second part of plate discipline.

Alright, so we know DeJong has made a change in what he’s swinging at. There’s just one important step left- actually hitting it. Well, easier said than done. The pitchers are trying to make you miss, after all. If you know one thing about Paul DeJong’s swing, you probably know that he swings violently and puts the ball in the air. You want the numbers? For his career, he’s hit 32.4% grounders when he puts the ball in play. Over the same time period, MLB average is just under 44%. Where are the extra balls going? Well, 43.3% of them are fly balls (league average 35%) and 24.3% are line drives (league average 21%). That’s great- that’s where the home runs come from. There’s just one issue here- that uppercut swing opens you up to swinging and missing. Want a visual? Take a look at this- Brandon McCarthy climbs the ladder well, and there’s no way DeJong is catching up to that with his swing:

Okay, so that’s a 2017 swing. Yet again, let’s see what DeJong did with an offseason to improve:

Swinging less, hitting the ball more often when he swings- there’s been a quiet revolution in Paul DeJong’s swing. Well, maybe it’s not so quiet. Here he is introducing Homer Bailey to the perils of pitching to a quick learner:

That’ll do; that’ll do. We can put these two things together and arrive at one last measure of plate discipline. All these elemental components are nice and all, but if you want a single measure of how hard someone is going to be to strike out, take a look at their swinging strike rate. What percentage of a time does a batter swing and not make any contact at all? If a lot of a hitter’s swings end up empty, it’s going to be a long season. If a batter is almost never swinging and missing? Well, good luck sneaking something by him in the zone, because that’s the only way you’re striking him out. DeJong’s improvement here is what we in the baseball analysis business call ‘very nice:’

For another data point, league average here is 10%. After being worse than league average pretty much all of last year, he’s been better than league average since the early part of this year. That’s a dangerous hitter right there.

Well, we took a reasonably deep dive into a bunch of things DeJong has changed about his game. Lots of graphs, lots of numbers, lots of averages. Let’s see the results, though. Let’s see the walks and the strikeouts. The proof of the pudding is in the eating, right?

This picture looked a little bit prettier before last night’s three-strikeout performance, but it still looks plenty good. After, again, an insane spike up at the beginning of this year, his strikeout rate has declined to a pretty stable rate around the major league average of 22%. At the same time, his walk rate has increased to around 8%. Now wait a second, you might be saying, how happy are we supposed to be that our supposedly much-improved player is now league average at strikeouts and walks? That sounds like a little bit of a letdown after a whole article of hype.

Well, if Paul DeJong was your average slap-hitting shortstop, I’d agree with you. The thing is, though, he’s not. He’s running an ISO of .227 for his career, comfortably above the .165 major league average and .149 shortstop average during that same timeframe. He also absolutely hits the crap out of the ball- that ISO is no fluke. Here’s a list of shortstops with a higher average exit velocity than Paul DeJong this year (minimum 100 batted balls): Manny Machado, Xander Bogaerts, Francisco Lindor, and Trevor Story. I’ll take that list and average plate discipline every day of the week. Those same four are the only four shortstops to barrel a higher percentage of pitches they’ve seen (for clarity, a ‘barrel’ is a Statcast definition that means a ball hit hard enough to have an expected batting average of at least .500 and slugging percentage of at least 1.500. You can read the definition here). The kid can rake, and now he can take a walk. It’s going to get more exciting from here.

I owe an epilogue here, because I wrote an article about DeJong suggesting that he hadn’t recovered from his broken pinkie. His power was way down, and in particular he was hitting way fewer balls over 100mph. Let’s take a look at how that’s changed in the last month. Here’s a graph of how many batted balls out of each 25-ball sample were hit over 100mph:

Looks like he fixed it. The drop to only one 100mph+ ball started on July 20th, if that gives you a better idea of a recent timeframe. Man it feels good to have a beast-mode Paul DeJong back. With someone as adaptable as DeJong, it was only a matter of time.

Stats current through Sunday, 8/19.