Name: Baseball's Secret Playbook: How Numbers Turned Scouting into a Superpower and Changed the Game Forever
Author: step-3.5-flash

What's Baseball Data, Anyway?

Have you ever watched a baseball game with a grown-up and heard them shout, “Wow, his exit velocity is 112 miles per hour—this is gonna be a home run!” or “Ugh, his batting average is only .220 this month, he’s in a slump!” and wondered what on earth they were talking about? Or maybe you’ve stared at the tiny stats box on the bottom of your TV screen during a game and thought those numbers were just boring math stuff, nothing to do with the fun of catching a foul ball or eating a churro at the ballpark. Spoiler alert: those numbers are baseball data, and they’re way cooler (and way more useful) than you think.

Baseball data is just any number or piece of information that describes what happens in a game, or what a player is good (or bad) at. It’s not just for math class, and it’s not just for team executives in fancy suits. It’s the secret language of baseball that helps teams pick the best players, make smarter decisions during games, and even helps fans like you enjoy the game more. In this chapter, we’re going to break down exactly what counts as baseball data, from the simple stats you’ve seen on the back of baseball cards for 100 years, to the super high-tech tracking numbers teams use today to win World Series. By the end, you’ll be able to impress your friends and family with your baseball data knowledge, and you’ll be ready to use numbers to become a better fan (and maybe even win your fantasy league!).

Let’s start with the stuff you already know.

The Stats You’ve Seen a Million Times: “Old School” Baseball Data

If you’ve ever collected baseball cards, watched a game on TV, or played *MLB The Show*, you’ve already seen old school baseball data. These are the classic stats that have been around since the early 1900s, when a guy in a newsboy cap sat in the stands with a notebook and pencil, writing down every single play by hand. No cameras, no computers, no fancy sensors—just a person with good handwriting and a love of baseball.

Every time a player hit a single, struck out, or stole a base, the scorekeeper wrote it down. At the end of the game, they added up all the numbers to calculate the basic stats we still use today. Let’s break down the most common ones, with examples you’ll recognize: 1. Batting Average (AVG): This is the most famous baseball stat, and it tells you how often a player gets a hit when they go up to bat. It’s calculated by dividing the number of hits by the number of official at-bats (walks and hit-by-pitches don’t count, because the player didn’t swing the bat!): $$\text{Batting Average (AVG)} = \frac{\text{Number of Hits}}{\text{Number of At-Bats}}$$ If a player gets 30 hits in 100 at-bats, their batting average is .300— and that’s considered really, really good in Major League Baseball! In 2023, only 18 players hit .300 or higher for the whole season, and the league leader, Ronald Acuña Jr. of the Atlanta Braves, hit an amazing .337. That means he got a hit more than 1 out of every 3 times he stepped up to the plate! 2. Home Runs (HR): This one’s easy—it’s the number of times a player hits the ball all the way over the outfield fence for an automatic run. In 2023, the New York Yankees’ Aaron Judge hit 62 home runs, the most in the entire league. That’s like hitting a home run almost once every 3 games! 3. Runs Batted In (RBI): This stat counts how many runs a player helps score by getting a hit, sacrifice fly, or walk with runners on base. If a player hits a single with a runner on third, and that runner scores, the hitter gets an RBI. In 2023, the league leader in RBIs was Cody Bellinger of the Chicago Cubs, with 97—that means he helped score almost 100 runs for his team that year! 4. Strikeouts (SO): This counts how many times a batter swings and misses at a pitch, or doesn’t swing at a pitch that was in the strike zone. Some power hitters strike out a lot because they swing really hard at every pitch; in 2023, Judge struck out 175 times, the most in the league. But if a player strikes out too much, it means they’re not hitting the ball enough to help their team score runs. 5. Earned Run Average (ERA): This is the most common stat for pitchers, and it tells you how many runs a pitcher gives up on average per 9 innings. It’s calculated like this: $$\text{ERA} = \frac{\text{Number of Earned Runs} \times 9}{\text{Number of Innings Pitched}}$$ If a pitcher gives up 3 earned runs in 9 innings, their ERA is 3.00. An ERA under 3.00 is great for a starting pitcher, and an ERA under 2.00 is amazing—like the 2023 Cy Young Award winner, Justin Verlander of the Houston Astros, who had an ERA of 3.15 that year. Wait, that’s not under 3.00? Oh, that’s because the league average ERA in 2023 was 4.28, so 3.15 is still way better than most pitchers! 6. Saves (SV): This stat is for relief pitchers, who come in to pitch the last few innings of a game when their team is winning by 3 runs or less. If they finish the game without giving up the lead, they get a save. In 2023, the league leader in saves was Edwin Díaz of the New York Mets, with 53 saves—that means he finished 53 games for his team without letting the other team take the lead!

These old school stats are still super important, and you’ll see them on every baseball card, every sports website, and every game broadcast. But they have a big problem: they don’t tell you *why* a player is good or bad. For example, if a player has a .230 batting average, is that because they’re a bad hitter, or because they’ve been hitting a lot of line drives right at fielders who catch them? Old school stats can’t tell you that. That’s where the new, high-tech data comes in.

The Cool New Data You’ve Never Seen Before: High-Tech Tracking Stats

In 2015, Major League Baseball rolled out a system called Statcast to every single ballpark in the league. Statcast uses 12 super high-speed cameras (they can take 1,000 pictures per second!) and 3 radar sensors installed around the stadium to track *everything* that happens on the field. Every pitch, every hit, every throw, every step a player takes is recorded by Statcast, and it collects more than 100,000 data points per game. That’s 100 times more data than the old school scorekeepers ever collected!

You’ve probably seen some of these stats on TV during a game, even if you didn’t know what they meant. Let’s break down the most common ones: 1. Exit Velocity (EV): This is how fast the ball is moving the second it leaves the bat, measured in miles per hour (mph). The average exit velocity in MLB in 2023 was 89.5 mph. If a ball has an exit velocity of 100 mph or higher, it’s a really hard-hit ball, and it has a very good chance of being a hit (or even a home run!). Aaron Judge’s average exit velocity in 2023 was 95.2 mph, which is one of the highest in the league—no wonder he hit 62 home runs! In 2022, a fan at a Houston Astros game caught a foul ball that had an exit velocity of 113 mph. That’s so hard, it broke the fan’s phone that was in his pocket! 2. Launch Angle (LA): This is the angle at which the ball leaves the bat, measured in degrees. A launch angle between 10 and 30 degrees is the “golden zone” for extra-base hits, because the ball will go far enough to get over the outfield fence, but not so high that it’s an easy pop fly for a fielder to catch. In 2023, Ronald Acuña Jr. had an average launch angle of 18 degrees, which is perfect for hitting home runs and doubles. If a ball has a launch angle of 0 degrees, it’s a line drive right at the ground; if it’s 45 degrees, it’s a high pop fly that’s easy for a fielder to catch. 3. Spin Rate (SR): This is how fast the ball spins as it flies through the air, measured in revolution