The Cure for the Home-Run Era

Home runs were everywhere last season! You might have heard. Conveniently, just as baseball was beginning to express concern that hitters didn’t have enough of a chance, balls started leaving the ballparks in record number. This was, naturally, examined over and over. One popular explanation is that baseball arranged to have the actual ball manufactured differently. A related and popular explanation is that the ball was manufactured differently kind of by accident. And then there’s the theory that hitters simply tried to hit more homers. You can see how that could lead to more homers.

That last theory gets tied into all the various swing-changers we’ve seen over the past few years. What if there are just more hitters than ever trying to hit the ball both hard and in the air? Anecdotally, it passes the smell test, and I should say I love being able to follow a relevant Travis Sawchik post. Travis just spoke with J.D. Martinez, one of the more well-known swing-changers. Martinez tries to hit the ball in the air every single time, which he didn’t used to do. Martinez seems to hold ground balls in contempt. This is, in short, the story of how Martinez turned around his own big-league career.

Travis tucked something in toward the bottom of his article. An excerpt:

While Martinez believes there is being progress made league wide, he already sees pitchers trying to combat his hitting philosophy.

“Pitchers are countering it right now. The pitchers are always ahead,” Martinez said.

What exactly are the adjustments being made to his swing path? Martinez and I had not, apparently, reached that level of trust.

“That’s one of things you don’t want to tell anyone,” Martinez said.

While Martinez would not reveal what he believes to be counter measures to his swing path, it appears pitchers are trying to elevate their fastballs against Martinez.

Travis is right, and while Martinez might prefer not to share his vulnerability with a writer, you can’t hide something like this from the competition. Over the past three years, Martinez has slugged .752 against pitches in the lower or middle thirds of the strike zone. He’s slugged .424 against pitches in the upper third of the strike zone. That gives him a difference of 328 points, which ranks sixth-biggest. He’s sandwiched by fly-ball-hitting Yoenis Cespedes, swing-changer Marlon Byrd, and swing-changer Justin Turner.

Let’s step back from discussing specific players. So many of these swing-changers have been engineering their adjusted swings to do better against pitches down. This recalls that discovery that was published in The Book, that fly-ball hitters do better against ground-ball pitchers. Ground-ball pitchers generally throw sinkers and two-seamers, and those pitches are generally low. Fly-ball hitters swing up to a certain extent. They don’t have level planes. It follows that it’s easier for a fly-ball hitter to make his desired contact when a pitch is down around the knees or the thighs.

All right. Let’s look at this very simply. Where did all those extra home runs come from last season? In this plot, home runs per swing, on pitches in the strike zone, where the zone is divided into thirds.

Homers on pitches in the lower third took off. Homers on pitches in the middle third also increased. Homers on pitches in the upper third…stayed the same. All that extra good contact was coming from the zone’s lowest 66%. In this table, a further simplified comparison:

In the table, I’m using 2008 – 2015 as the baseline. Relative to that, homers in the lower third went up 0.6 percentage points. Homers in the middle third went up 0.4 percentage points. Homers in the upper third went ever so slightly down. My suspicion is that, if the home-run spike were all about the ball, we’d see more even distributions in places like this. The fact that the evidence is instead what it is suggests that, at least in part, this comes from a collectively different approach.

It makes sense for more hitters to be trying to get better at hitting low pitches. There are plenty of pitches down there.

Yet look in here at how contact rates have changed.

Contact was down against pitches in all three of the upper in-zone boxes. Contact held more steady against pitches in the other six in-zone boxes. This plot of slugging percentages also shows a similar pattern:

This was basically already demonstrated by the earlier plot. Slugging went down against pitches up. It went up against pitches down. It’s not proof of anything much, but it’s strongly suggested there was a broad adjustment being made, broad enough to show up in league-wide statistics. The power spike came from production against pitches in the middle and lower thirds. Those are the pitches easiest to drive for hitters with uppercut swing paths. Those same hitters, with that same approach, have more trouble against pitches up. The pitches are harder to hit, and harder to hit well, because the bat has more distance to travel, and big-league pitches move quick.

So for pitchers feeling spooked, there’s the hint of a solution in here. And it’s something we’ve discussed before, with regard to the big picture, and with regard to Mike Trout. Conventional wisdom has said the best swing is a level one. In truth, the best swing is a swing up. And, conventional wisdom has said the best way to avoid a home run is to pitch down. In truth, at least now, it’s probably to pitch up. High fastballs are associated with homers, but they should really be associated with pop-ups and empty whiffs. The swing-changers, the power-hitting revolution — it’s all designed to combat how pitchers have gone on the attack. Pitchers can change how they attack if they want. The more a hitter swings up, the more he can probably be exploited around the belt. Baseball can seemingly never just stand in one place.