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How to Analyze a Hitter's Baseball Savant Page

Astros DH/LF Yordan Alvarez; CC BY 2.0

Baseball Savant is one of the most useful tools for hardcore baseball fans to research player analytics and check in to see how players are doing. It is a great collection of metrics that baseball fans and statheads like me love. However, a lot of people are overwhelmed by the sheer amount of data on a Baseball Savant page or just look at the famous red or blue bubbles to see how good a player is. Since diving headfirst into a Savant page with no experience can be intimidating, I have written part one of a two-part guide on how to properly analyze a Baseball Savant page and separate useful information from eyewash. This edition focuses on hitters. The second part will overview pitchers.

There is a lot of data on Baseball Savant, but it gets pretty complicated. In the interest of keeping things simple, this guide only focuses on the main graphic on an individual player’s Savant page, which is the most basic graphic that Savant users typically default to and is pictured in the section below.

The Bubbles

The most famous part of a player’s Baseball Savant page is the bubbles you see when you first open the page. A screenshot of a graphic featuring these bubbles is the go-to evidence in any kind of Twitter argument. For those who do not know, the bubbles are a series of percentile rankings in different stats. The higher the percentile, the better that player is in that stat. These bubbles also have an associated color that lies on a gradient between dark blue and dark red as a visual aid to make them easier to read. Blue means lower percentile ranks, while red means higher. Here is an example of Yordan Alvarez’s bubbles from thus far into the 2024 season. 

A lot of metrics are thrown into that one graphic. Here are explanations for them all.


The bubble graphics begin with the three value stats: Batting, Baserunning, and Fielding. These are simple to understand: they measure the number of runs a player has added or subtracted. A value of positive 5 indicates 5 runs added, while a value of -5 means the player lost 5 runs. These stats are similar to WAR in that they give one number to measure the overall value of the player, but it is divided into three facets: batting, fielding, and baserunning. Value is a quick and easy way to see everything a player brings to a team among different aspects of the game. 


The batting section of the Baseball Savant page is the most extensive and most commonly used section when analyzing hitters. The section starts with three expected stats: xwOBA, xSLG, and xBA. All these expected stats use Statcast data, which tracks the speed and launch angle of the ball off the bat, to estimate the probability of each batted ball becoming a hit or an out. Those probabilities are then used to form what the player’s metrics (wOBA, SLG, and BA) are “expected” to be, forming xwOBA, xSLG, and xBA. xwOBA (and all expected stats) are more nuanced than normal versions and remove the effect of luck on player evaluation. A player with a high xwOBA but a low actual wOBA might be experiencing bad luck, while a player with a low xwOBA but a high actual wOBA typically has some good luck. This same principle goes for xBA and xSLG as well.

Next is Average Exit Velocity. This is simply the average of all exit velocities on a player’s batted balls. This is a useful metric because the harder a player hits the ball on average, the better the player typically performs over a large sample size. 

The next three stats used are the three quality of contact stats: Barrel%, Hard-Hit%, and Sweet-Spot%. A barrel in the analytical world is classified as the optimal combination of exit velocity and launch angle on a batted ball. Barrels typically result in a well-struck ball with a high likelihood of producing positive offensive outcomes, such as extra-base hits or home runs. Barrel% is the percentage of batted balls that are barreled. Hard-Hit% is the percentage of batted balls that are hit hard (exit velocity above 95 mph). The last of these metrics is Sweet-Spot%, which measures the rate at which a hitter makes contact with the ball in this optimal zone (the “sweet spot”) relative to their total batted ball events. Hitting the sweet spot is defined as producing a launch angle on a ball between 8 and 32 degrees. These three stats are valuable metrics for evaluating a hitter's quality of contact and predicting their offensive performance. Higher-quality contact typically leads to more power and better outcomes at the plate, while poor contact is usually indicative of an unproductive hitter. 

The last grouping of the Batting section is Chase%, Whiff%, K%, and BB%. Chase%, also known as O-Swing% (Swings on Pitches Outside the Strike Zone), measures the rate at which a hitter, well, swings at pitches outside the strike zone. A high Chase% indicates that a hitter has poor plate discipline, which can lead to more strikeouts and fewer walks. It indicates that the hitter is either easily fooled by pitches or struggles to lay off pitches that are not hittable. Conversely, a low Chase% suggests that a hitter has better plate discipline and is more selective about the pitches they swing at, which can lead to more favorable counts, better pitches to hit, and ultimately more success at the plate. Whiff%, also known as Swinging Strike Percentage or Swing and Miss Percentage, measures the rate at which a hitter swings and misses at pitches. Whiff% provides insight into a hitter's ability to make contact with pitches. A high Whiff% suggests that a hitter struggles to make contact and may have holes in their swing or difficulty recognizing pitches. Conversely, a low Whiff% indicates that a hitter makes more consistent contact with pitches, which is generally associated with better hitting ability and a lower likelihood of strikeouts. Lastly, K% and BB% simply show the percentage of at-bats that end in a K or BB. These metrics are better than the cumulative count of Ks or BBs because they can normalize it for players with different amounts of PAs. 


Next are the three fielding stats: OAA, Arm Value, and Arm Strength. OAA (short for Outs Above Average) is one of the most important defensive stats. OAA is based on tracking data, often provided by Statcast in Major League Baseball. This data captures the initial direction, velocity, and hang time of each batted ball, as well as the fielder's positioning and reaction. Using this tracking data, an expected outcome is determined for each batted ball based on the aforementioned factors. For example, a well-hit line drive with a low launch angle has a high probability of becoming a hit, while a weakly hit pop-up has a high probability of being caught. OAA compares a fielder's actual performance to these expected outcomes. If a fielder makes a play that is more difficult than average based on the expected outcome, they are credited with an "Out Above Average." Conversely, if they fail to make a play that was easier than average, they might be docked for that. This is the best defensive stat we have access to right now. The last two stats, arm value and arm strength, are both used in the value of runs added. They simply measure the impact a player's arm has on the game. A positive run value is given to a plus arm, and a negative value indicates a poor arm. They are not as used as OAA or as important but they still provide useful insight. 


The Running section only has one stat: Sprint Speed. Sprint Speed is measured using Statcast, a high-speed tracking technology installed in all MLB stadiums. Statcast captures the time it takes for a player to run from the moment the ball is hit or the player starts running, depending on the context, to a specific point on the field. This time is then converted into a speed measurement in feet per second. The specific distance covered varies depending on the situation being measured. For example, when measuring a player's sprint speed on the basepaths, it might be the distance between two bases. When measuring a player's outfield defense, it might be the distance covered to make a catch. Sprint Speed can provide insights into a player's performance and development over time. Changes in Sprint Speed values might indicate improvements or declines in a player's physical abilities. Overall, Sprint Speed is a useful metric for quantifying a player's speed and athleticism in baseball, providing valuable insights for player evaluation, performance analysis, and strategic decision-making.

Understanding and effectively analyzing the data presented on a Baseball Savant page is a valuable skill. While the sheer amount of information available may seem overwhelming at first glance, breaking down each component allows for a deeper understanding of a player’s performance and contribution to the game. The bubbles, with their percentile rankings and color-coded visual aids, provide a quick snapshot of a player's overall value and performance in batting, baserunning, and fielding. These metrics, such as expected statistics, quality of contact, and plate discipline indicators, offer insights into a player's skill set beyond traditional stats like batting average or fielding percentage.



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