The most improbable home run I’ve ever watched in real time was hit last November. You know the one — it was the one hit by Rajai Davis, against Aroldis Chapman, with Davis choked halfway up the barrel. I’m sure that, mathematically, there have been home runs of a lesser likelihood, but that Davis blast just felt impossible. It didn’t feel real until the ball cleared the fence. I still can’t believe it happened, and the Indians still lost the game a couple innings later. I don’t care. I recall the Davis home run more clearly than anything else.

In truth, in my book, any home run against Chapman counts as improbable. I don’t know how he ever gets touched. And yet, Davis, at least, was batting right-handed. He had the platoon advantage. And the pitch he lined out to left field clocked in at a hair over 97 miles per hour. Fast, but not *outrageously* so. There are plenty of pitchers out there who can throw 97. Sometimes they give up dingers. The Davis home run, realistically, never should’ve happened, but I can bring myself to get it. I can understand the mechanism.

When Davis took his hopeful swing, Rafael Devers was, I don’t know, somewhere. Probably, he was watching. But no matter what he was doing, he was doing it having recently turned 20 years old. He was a good baseball prospect, but he was one who hadn’t yet encountered Double-A competition. I’m not sure how close Devers felt like he was. Yet Sunday night, you could say that Devers arrived.

Even before Sunday, Devers was doing pretty well. He’d advanced through Portland, he’d advanced through Pawtucket, and he’d run a .939 OPS over some dozens of chances in the major leagues. Devers, as a rookie, has taken a firm hold on the Red Sox’s third-base position, which earlier had proven a crippling weakness. Now, though, Devers truly has his breakthrough moment. See, he batted against Chapman in the ninth inning of a one-run game, and he tied it up. He tied it up with a home run back up the middle, and he tied it up with a home run against a pitch measured at 102.8.

Pitchers have been throwing pitches for more than a hundred years. Batters have been swinging at them for same. And yet, for more than a century, we lacked all the data. We have pitch velocities tracked only back to 2008. So be it. We’re given a limited window, but still a meaningful one. For shorthand, you could say we have a decade of information. Over that decade, no one has gone yard against a faster fastball. Faster pitches have been thrown, but none of them have gone for four bases. Devers is still looking ahead to his 21st birthday, but already he’s done one of the most incredible things he’ll probably ever do.

The pitch was faster than the pitch thrown to Davis, by almost six ticks. And, unlike Davis, Devers went up batting left-handed. Chapman, historically, has been good against everyone, but he’s been the best pitcher against lefties on record. Using the Baseball Reference Play Index, I searched historical splits for pitchers who’ve thrown at least 100 innings against left-handed hitters. Chapman ranks first in slugging percentage against, at .174. The guy in second place is all the way up at .238. Then you’ve got a guy at .240. Chapman has faced 422 career lefties. Devers just doubled the home-run total.

This all is as absurd as it sounds. The following plot was generated using information from Baseball Savant. I examined the past decade and calculated the rate of home runs per batted ball, grouped by pitch velocity. Your eyes will be drawn to the right-hand column:

That’s not difficult to understand — it’s hard to hit a fast pitch out. Batters, often, will choke up or shorten their swings, just for the sake of making contact. And that’s the other part that isn’t shown. This includes the rates of home runs per batted ball. It says nothing about the rates of batted balls per swing attempt. The fastest pitches are hard to hit, and they’re hard to hit hard. Devers did a rare thing as the chyron flashed 103.

The fateful pitch was the fourth of the at-bat. Devers and Chapman had never before faced off, so we might as well go through the showdown pitch by pitch. Here is how it all began:

When I used to play, I was neither a good hitter, nor a thoughtful one. But I fancied myself a thoughtful one, because I always stuck with one particular bit of strategy. No matter who was on the mound, no matter how things were going, I’d always take the first pitch. I’d let the pitcher show me something, and I’d thus be able to help my own timing. I was terrible, so it didn’t work, but I figured it must’ve done something. If nothing else, getting me out always took at least two pitches.

At the major-league level, you can’t always take the first pitch. Opponents will notice, and then they’ll get ahead. Passivity is an observable weakness, and this is how a guy like J.J. Hardy can get himself in trouble. We’re starting to see something of a pushback; at least anecdotally, leadoff hitters appear to be more aggressive than ever before. Batters need to be ready to bat. Pitchers can’t know what you’re going to do in advance of throwing a pitch. That shifts the balance of power.

Devers couldn’t let Chapman know he wasn’t going to swing. Devers needed Chapman to believe there was some chance he’d take a hack. But, let’s be real, here. Was there any chance Devers was going to take a hack? How do you swing at the first pitch you ever see from Aroldis Chapman? You need to make sure you’re even able to see the baseball first. I can’t imagine what that experience is like. Devers needed to convey he might swing. Devers was probably never going to swing.

On it went:

There are a couple of ways you can take this. Sure, it’s possible that Devers simply identified the location and held up. It’s a good check-swing, and as a result, the count drew even. It’s always good to take a ball. If you want to see Devers for his best, you accept that he took this ball on purpose. The alternate interpretation is that Devers realized he was going to be way too late anyway. That he hadn’t gotten his timing all the way there. You be the judge. How the heck should I know? At 0-and-1, Devers held up. At 1-and-1, Devers took a rip.

The swing before The Swing, if you will. Chapman was throwing as hard as he ever has, and he was showing no signs of slowing down. Devers was trying to meet that velocity, and at 1-and-1, Devers figured the solution was to fight power with power. It’s an aggressive swing, an over-aggressive swing, and Devers comes away looking unbalanced. Baseball people the country around have praised Devers for his clean swing at 1-and-2. You’re about to see it for yourself. But the preceding swing was fairly ugly. For Devers, the at-bat was a learning experience.

The fourth pitch, I guess, was the final exam.

It’s available here in slower motion:

With no hyperbole intended, that swing is perfect. I mean, that’s easy enough to say, because the result was a home run toward center field, and any home run toward center field is likely to be the result of a swing with few flaws. But between successive pitches, Devers made an adjustment. It’s not so easy to see with screenshots, but we can give it a go. Here are the final three pitches of the at-bat, the pitches where Devers at least thought about swinging:

Look at Devers’ front leg. More specifically, look at Devers’ front leg, compared to his back leg. You can see a gap between them in the screenshots for the first two pitches shown above. In the third screenshot, the bottom one, Devers takes more of a clean step forward. He gets his foot down a hair sooner, and he also doesn’t open up. With Devers’ checked swing, and with his first full swing, you see the hips fly open. Devers, again, was trying to meet Chapman’s power with his own. With Devers’ second full swing, the one that knocked the ball out, he tweaked to a quieter, up-the-middle approach. The feet didn’t open, and the hips didn’t open. Devers increased his own margin of error, and he hit the ball square. There’s nothing too dramatic here, no conspicuous choking up on the bat; Devers realized Chapman had thrown only fastballs, and he realized he probably wasn’t going to get ahead of one. So he tried to go to center field instead of right, and the adjustment paid off.

Devers was greeted warmly in his own dugout:

Pitching coach Carl Willis was thrilled to have the game tied. Like everyone else in the dugout, Willis was overcome by emotion, and so he gave Devers his due. The kid had pulled off a borderline miracle. This was no time for the silent treatment.

Moments passed. Willis looked elsewhere as reality dawned. How to coach pitching when rookies are going yard against one hundred and three? For a fleeting instant, the future of baseball revealed itself. Willis mulled his next chapter. The present one is doomed.

Now, for all the celebration, I should say a couple more things. Devers went deep against 102.8. The previous high was 102.6, a pitch thrown last June, also by Aroldis Chapman. And the effective velocity of that previous pitch was 104.2. The effective velocity of the pitch hit out by Devers was 102.9. Chapman released the earlier pitch about six inches closer to the plate, which meant the pitch spent a fraction of a fraction of a second less time in the air. Technically, you could argue that’s the fastest pitch hit out. All this information we have access to these days renders certain records debatable. And also, oh, that previous home run, off the pitch at 102.6? It was hit by Kurt Suzuki.

That’s an awfully good swing, but no one would say that Kurt Suzuki is an awfully good hitter. The third-fastest pitch hit out on record was hit by Tyler Greene. The fourth-fastest pitch hit out on record was hit by Jose Lopez. Going deep against heat doesn’t mean you’re a superstar. Going deep against heat means you caught up to the heat. As they say, everyone in the majors can hit a fastball. The separator is the other stuff.

But I don’t mean to diminish the accomplishment. No, Rafael Devers hasn’t cemented himself as a future Hall-of-Famer. He still did hit an unbelievable home run. Batting lefty against the best southpaw in recent history, Devers found his timing mid-at-bat and took 102.8 miles per hour to the deepest part of the ballpark. I’ll never forget what Rajai Davis was able to do. As for the Devers home run, I might just never believe it.