Expanding the Strike Zone for Fun and Profit

Jose Altuve
Troy Taormina-USA TODAY Sports

Ask pretty much any major league hitter, and they’ll tell you that they earn their paycheck with runners in scoring position. A base hit means a run, and you have to score runs to win games. An out — particularly a strikeout — squanders an opportunity to score, and those come vanishingly rarely these days, what with every pitcher in baseball throwing 100 mph with a wipeout slider and all. It’s the highest-leverage spot you can hit in; succeed with runners in scoring position, and your team will probably win, but fail, and it’s going to be a long night.

As far as we can tell, success in those situations — runners in scoring position, high leverage, you name it — isn’t predictive of future success. But that doesn’t mean approach isn’t predictive of future approach, and as you might imagine, hitters behave differently when they can smell an RBI opportunity.

One easy way to conceptualize this change in approach is to think of the edges of the zone and the area just outside of the strike zone — the Shadow Zone, in Statcast parlance — as a good test of what a hitter wants to do. On pitches down the heart of the plate, swinging is a clear best choice. On pitches nowhere near the zone, taking is the only right choice. But pitches that could go either way? The best strategy depends on what you’re trying to accomplish.

With runners in scoring position and no one on first — in other words, a situation where a walk is far worse than a hit — major leaguers have swung at shadow zone pitches 56.4% of the time (in the last two years). On the whole, they’ve only swung 52.9% of the time at those pitches. In other words, they increase their borderline pitch swing rate by 3.5 percentage points when the gap between a walk and a single is the largest.

That’s a rather unimpressive number. It’s the clearest time to swing that you can imagine, and batters are hardly changing their behavior. But that’s logical, when you think about it. Walks aren’t suddenly worthless just because you could drive in a run; juicing up the bases for the next batter still has value. And swinging at borderline pitches is hardly the best way to drive in runs; taking borderline pitches and waiting for a mistake, or for the pitcher to challenge you, might be a better decision.

But just because that’s true in the aggregate doesn’t mean it’s true for every hitter. Hanser Alberto swings at 81.7% of the pitches he sees in the shadow zone when there are runners in scoring position. If you throw him something he could conceivably get his bat on, he’s going to try. Sure, he swings a lot — at 72.7% of pitches in the shadow zone overall — but put a runner in scoring position, and he truly takes it into overdrive.

Alberto isn’t alone in his aggression. In fact, plenty of hitters are even more aggressive than he is. Thirty-two hitters have increased their swing rate by at least 10 percentage points with runners in scoring position and no one on first base, ranging from powerful (Luke Voit and Brandon Belt) to slap hitters (Nick Madrigal and David Fletcher). These hitters should be easy marks for opportunistic pitchers. They’re not up there taking; they’re looking for a pitch to drive, or at least something to punch the other way. The correct counter for pitchers seems quite clear to me: don’t give them anything to hit.

Do pitchers do that? Not exactly. That cohort of batters saw pitches right down the middle 26.6% of the time overall in my sample, games in 2021 and ’22. With a runner in scoring position and first base open, that number declined… to 25.6%. That’s actually less of a decrease than the league as a whole sees.

So are these aggressive hitters beating the system? In essence, yes. Here’s a chart that you’ve certainly seen versions of this year: run value based on swinging or taking in various parts of the zone. As Justin Choi put it, maybe hitters should just stop swinging. This chart displays run value above average per 100 pitches for each zone/swing decision combination, and it shows the downsides of taking a cut:

RV/100, MLB
Zone Swing Take
Heart 0.27 -5.56
Shadow -3.12 0.10
Chase -7.69 5.74
Waste -11.48 5.25

As Eno Sarris reported, front offices and players alike are starting to discover that hitters swing too much. It’s a widely accepted fact at this point; the issue is how to train hitters to swing less while still maintaining enough aggression to keep pitchers from battering them in the zone.

That’s all well and good, but with a runner in scoring position and first base open, the math changes:

RV/100, RISP, 1B Open
Zone Swing Take
Heart 1.68 -7.54
Shadow -2.54 -0.91
Chase -9.32 5.65
Waste -18.02 5.37

These run values take the base/out situation into account. Getting closer to a walk matters less when the walk is less valuable. Hitting a deep fly ball is more likely to score a runner. A single in the gap is worth exponentially more when it drives in a run than when the bases are empty. The value of a ball in play isn’t static, which means the value of a swing isn’t static.

Working out the exact value of these extra swings is beyond the scope of this analysis, because it’s a bit more complicated than summing up the run values and multiplying. Even without a specific number, though, I can say this: our group of aggressive swingers are onto something. Taking a pitch down the middle when balls in play are valuable is the absolute worst thing you can do. Converting a single down-the-pipe take into a swing is worth plenty of extra swings at worse pitches, particularly those shadow zone swings where there are no good outcomes for the hitter anyway.

The league as a whole certainly understands this. But not every hitter does. Just as there’s a group of hitters who increase their aggression the most when there are runners to be driven in, there’s a group of hitters who swing less at borderline pitches in these situations. The biggest name there is an unexpected one: Jose Altuve.

In his career, Altuve has displayed the behavior you’d expect from someone with his blend of contact and power. Give him runners to drive home, and he raises his swing rate across the board, particularly at pitches down the middle. This just in: Jose Altuve is a very good hitter. Since the start of 2021, however, he has been doing the opposite of what you’d expect. He swings at 55.2% of shadow zone pitches overall, but only 47.9% when there are runners in scoring position and no one on first.

Is Altuve simply not aggressive enough for his own good? Not exactly. He’s still dialing up the aggression where it matters most, over the heart of the plate. And he’s dialing down his aggression when it’s worst, swinging at fewer bad pitches in important situations. In other words, he’s just been better when it matters most. Is that sustainable? Probably not. Is it some innate skill? I don’t think so; he hasn’t demonstrated it over the course of his career, for example. But for now, Altuve is locked in.

Does all of this mean anything? I think the broadest possible conclusion is probably the right one. Batters are good at internalizing the importance of count. They might swing too much overall, but from whatever baseline they start at, they generally understand how to change their behavior to respond to changing incentives. They can’t all be like Altuve — even Altuve doesn’t do this consistently — but they can at least think swing more often in good spots and let the chips fall where they may.

Listen to enough games, and you’ll hear plenty of announcers telling you that situational hitting is dead. To some extent, they’re right. It’s harder than it used to be to keep the line moving, or hit one the other way to help advance the runner, or whatever other cliche you’d like to use. But batters aren’t sitting there and accepting their fate. They’re trying to do exactly what everyone wants them to do: swinging more often, trying to make something happen. The numbers prove it: even if they don’t succeed, hitters are still as interested in RBI and timely balls in play as they’ve ever been.

Ben is a writer at FanGraphs. He can be found on Twitter @_Ben_Clemens.

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