What is Statcast and what baseball data does it measure and record?
Statcast has gone from being a simple tool to help collate data for television and MLB fans to becoming the final word in baseball. But what exactly is it?
As hard as it may be for the younger baseball fans to believe, such revered categories as exit velocity or launch angle, tools that are the focus of so many young hitter’s training regime, simply did not exist ten years ago. They were conjured into existence by a system so ubiquitous, so all-encompassing, that it is almost synonymous with baseball itself. Statcast.
There was a time, not all that long ago, when a player who hit a ball hard was judged on how it felt, how it looked, and how it sounded. Of course, pitchers were measured with radar guns, since the 1980s at least, but every other player was simply judged by the way they seemed to play the game.
All of this crept slowly forward with the 2006 introduction of the PITCHf/x system, which used three cameras to judge the spin, trajectory, break, and location of each pitch with an accuracy of one mile per hour and one inch. In 2014, Statcast was unveiled at MIT and began to be used in the 2015 season.
Statcast consists of two, rather than three cameras, mirroring the human eye’s binocular vision. The cameras are provided by Hawk-Eye Innovations, the same company that has provided high speed cameras for similar applications in cricket, tennis, and soccer. With each stadium having 12 cameras arrayed around the ground, all of the movements of both ball and players can be monitored, and with a coupling with radar speeds of batted balls as well as thrown ones can be measured.
By tracking and quantifying such a large amount of the action, the data gathered for each game is on the order of seven terrabytes of Google Cloud space.
Measurements that Statcast makes include:
- Arm Strength: How hard, in miles per hour, a fielder throws the ball.
- Base-to-base Time: How much time, in seconds, it takes a runner to get from one base to another, like Home To First.
- Distance Covered: How far, in feet, a fielder or runner has traveled on a play.
- Extension: How far off the mound, in feet, a pitcher releases the pitch.
- Exit Velocity: How fast, in miles per hour, a ball was hit by a batter.
- Launch Angle: How high, in degrees, a ball was hit by a batter.
- Lead Distance: How far, in feet, a runner is ranging off the bag at the time of a pitcher’s first movement or pitch release.
- Pitch Velocity: How hard, in miles per hour, a pitch is thrown.
- Pop Time: How quickly, in seconds, a catcher can get the ball out of his glove and to the base on a stolen base or pickoff attempt.
- Spin Rate: How much spin, in revolutions per minute, a pitch was thrown with.
Metrics include:
- Barrels: A batted ball with the perfect combination of exit velocity and launch angle, or the most high-value batted balls. (A barrel has a minimum Expected Batting Average of .500 and Expected Slugging Percentage of 1.500.)
- Catch Probability: The likelihood, in percent, that an outfielder will be able to make a catch on an individual batted ball. Catch Probability accounts for distance needed, time available, direction, and proximity to the wall, compared to how often the same opportunity is caught by Major League outfielders. This allows Statcast to get past the eye test and say “that ball gets caught 95 percent of the time,” for example.
- Expected Batting Average (xBA): xBA measures the likelihood that a batted ball will become a hit. Each batted ball is assigned an xBA based on how often comparable balls -- in terms of exit velocity, launch angle and, on certain types of batted balls, Sprint Speed -- have become hits since Statcast was implemented Major League wide in 2015. By comparing expected numbers to real-world outcomes over a period of time, it can be possible to identify which hitters (or pitchers) are over- or under-performing their demonstrated skill.
- Expected Weighted On-base Average (xwOBA): xwOBA is formulated using exit velocity, launch angle and, on certain types of batted balls, Sprint Speed. In the same way that each batted ball is assigned an xBA, every batted ball is given a single, double, triple and home run probability based on the results of comparable batted balls since Statcast was implemented Major League wide in 2015. xwOBA also factors in real-world walk and strikeout numbers, and is reported on the wOBA scale. By comparing expected numbers to real-world outcomes over a period of time, it can be possible to identify which hitters (or pitchers) are over- or under-performing their demonstrated skill.
- Outs Above Average (OAA): A range-based metric of skill that shows how many outs a player has saved over his peers. Prior to 2020, OAA was an outfield-only metric. But it has been expanded to include infielders. OAA is calculated differently for outfielders and infielders.
- Sprint Speed: A measurement of a player’s top running speed, expressed in “feet per second in a player’s fastest one-second window.” This can be delivered on individual plays or as a season average, found by finding all qualified runs (currently defined as anything two bases or more, excluding homers) and averaging the top half of those. In 2017, Buxton led the Majors with a Sprint Speed of 30.2 ft/sec, while the Major League average was 27 ft/sec.
By providing such a staggering amount of data, much of its usefulness hotly debated, organizations have seen outcomes in certain areas, such as power hitting, improve greatly, while other, more tactical parts of the game, often suffer from over-cautiousness. Fantasy leagues are far more informative, but baseball is in danger of information overload, becoming in the words of Bill James “as much fun as doing your taxes.”
Statcast itself is a great tool, even if the over-reliance on it by fans, pundits, and more worryingly front offices is not. Rather than ask how hard someone hits we should look at how well they hit. Without the technology to back it up, the best players still managed to do alright for a long time by simply hitting it where they ain’t.