Gary A. Vasquez-USA TODAY Sports
Over the past month, smart people have been deciphering the relationship between swing length and pitch location in MLB’s new bat tracking data. If you’re looking at raw data, it’s hard to know whether someone has a long swing because they like inside pitches (Isaac Paredes) or because their swing is actually long and loopy (Javier Báez).
In order to make solid contact with an inside pitch, the barrel needs to meet the ball out in front of the plate, which means that it will take a longer journey to the point of contact than it would to meet a pitch over the middle of the plate. Below is a breakdown of Luis Arraez’s swing length against fastballs.
As you can see, even the king of the short swing gets long when he has to reach pitches up-and-in or down-and-away. Some of this is as old as the game itself. It’s the reason pitchers throw fastballs up and in, where a necessarily longer, slower swing makes them harder to catch up with.
Bat tracking has given us numbers to back up another intuitive part of the game: Swing length is positively correlated with bat speed, confirming that players who are short to the ball sacrifice bat speed for bat control and contact ability. Those two correlations, pitch location to swing length and swing length to bat speed, got me thinking about the launch angle revolution.
The launch angle revolution really got its hooks into Major League Baseball in 2015. That’s the year Joey Gallo and Kris Bryant debuted, and the year Justin Turner and Daniel Murphy fully turned themselves from contact hitters into power threats.
In The MVP Machine, Ben Lindbergh and Travis Sawchick documented what Turner was thinking in 2013, the very first time he tried out the new approach for which teammate Marlon Byrd had been proselytizing. “I was thinking, I’m just going to try and catch the ball as far out as I can in batting practice,” Turner said.
Catching the ball out front often means pulling it, especially in the air. The league’s overall pull rate is roughly the same as it was in 2011, but as you can see from the chart above, its pull rate on air balls — the line drives and fly balls where hitters do damage — hit an all-time high in 2017 and then again in four of the next five years.
The exact approaches can differ. “I’m going to be on the fastball and drive it to right center, and if I’m a little early on the slider I’ll catch it out in front,” Austin Riley told Eno Sarris last year. And as Ben Clemens has noted, hitters have increased their pulled balls in the air simply by choosing to attack pitches that lend themselves to being launched in that direction.
But strictly speaking, there isn’t a huge inherent advantage to pulling the baseball. If you’re going to hit a long fly ball, it’s better not to hit it to straightaway center, where the fence is deeper and the fielders are better, but that’s equally true for both pulling the ball and going the opposite way.
In a sense, pulling the baseball is just a side effect of catching the ball out in front. There are two main benefits to catching the ball out in front. Naturally, the most famous benefit is an increase in launch angle. In any but the most dramatic of old-fashioned, chopping-wood-style swings, attack angle will drop at the beginning of the swing, then increase toward the end.
To illustrate that down-up-down path, I slowed down a Statcast video showing Oneil Cruz’s bat path on a recent line drive. If you meet the ball out in front, your bat is more likely to be moving upward, which means you’re more likely to put the ball in the air. Doug Latta, the swing guru who trained Byrd, preaches getting on plane with the ball early, which is to say moving your bat through the zone to meet it at an upward angle.
That’s usually what we mean when we talk about the launch angle revolution: meeting the ball out in front in order to put it in the air. But the bat tracking data make it clear that we might have been focusing on the wrong part of that approach.
At this point, let’s stop to remember exactly how Statcast measures bat speed. It’s the speed of the barrel (the spot six inches from the end of the bat) in the last video frame before the bat impacts the ball. In the case of a miss, it’s measuring the speed of the barrel in the frame when it’s closest to the ball.
But here’s the thing: When a player swings, they don’t have one exact bat speed. Their bat speed is increasing throughout the swing, and the number we’re getting comes at the point of contact. Since we know that pull contact happens out in front and oppo contact happens deeper, batted ball direction is our best proxy for contact depth.
That’s why I started thinking about the launch angle revolution. The bat tracking numbers have made it more clear than ever that the other benefit of meeting the ball out in front is that you can hit the ball harder because your bat is moving faster.
We have known this for a while, sort of. At any point in the Statcast era, you could do a quick search comparing exit velocity on balls that were hit to the pull side, straightaway, or the opposite field. This year, those numbers are 90.6 mph, 89.7, and 85.2, respectively.
Here at FanGraphs, we’ve noted those numbers many times and written a huge number of articles about the value of pulling the ball in the air. Ben Clemens writes an article about Isaac Paredes roughly six to eight times a week (including one this morning!). But I don’t know if I’ve ever heard anybody connect the dots all the way.
Seriously, read this long article about the launch angle revolution. Or read this one, or this one, or this one, or this one, or this one, or maybe this one from Mike Petriello, which comes so very close. “Indeed, all else equal, a pulled fly ball is by far the most productive batted ball,” wrote Alex Chamberlain back in February.
But just as I have done in my own articles, he didn’t quite hammer home the reason for it. “Why? Hitters generate more power to their pull side, and — if you perhaps haven’t watched a game of baseball before — the shortest distance to the outfield walls is down the lines, toward the foul poles, rather than to straightaway center field. It’s a twofold recipe for success.”
Why do hitters generate more power to their pull side? No matter where I’ve looked, I haven’t seen anybody say it plainly: Hitting the ball out in front means hitting the ball harder because that’s when your bat is moving fastest.
Here’s what Doug Latta (of all people!) said when Laurila asked him about exit velocity directly: “There are a lot of people trying to train, ‘hit the ball hard, hit the ball hard, hit the ball hard.’ What generally comes out of that training is swings, bad movements, that don’t translate to seven o’clock at night. We talk a lot, here, about tempo and reduced effort, which flies in the face of exit-velocity teaching.”
In an interview with Sawchick, he said that his method increased exit velocity simply because it allowed the batter to square up more balls. Well, now we can check the numbers. Here are the exit velocities and bat speeds on balls that were squared up this season.
Squared-Up Balls In Play
Metric Pull Straight Oppo
Exit Velocity 97.5 96.4 93.1
Bat Speed 72.3 70.8 69.1
