STATS TVL Determines 2018’s Best Arms

Part of the beauty of pitching is there are multiple avenues a pitcher can travel to find success.

To analyze how pitchers arrive there, STATS uses TVL data (pitch Type, Velocity and Location) to explore efficiency on the mound and at the plate.

Using this data, STATS created expected Run Value Above Average (xRVAA-), which considers several different methods, evaluates the success a pitcher finds with each of them, and generates a final performance metric based on runs prevented on a per pitch basis. xRVAA- is broken down into the following components:

1. Command (Command+)
2. Generating bad decisions by the hitter (Discipline-)
3. Generating whiffs (Whiff+)
4. Inducing bad contact (BIP-)

Discipline-, Whiff+, and BIP- evaluate the effectiveness of a pitcher at different stages within the process of a pitch. Discipline- looks at how well the pitcher “fools” a hitter into swinging at a ball or taking a strike. Once a hitter decides to swing, Whiff+ evaluates how often the pitcher can turn those swings into a swing and miss. If a hitter does make contact, BIP- is used to consider how good a pitcher is at limiting the quality of that contact.

Unlike the metrics mentioned previously, Command+ evaluates just the pitcher, describing the ability of the pitcher to hit his spots. STATS collects a data point called Pitch Intent to describe the intended location of each pitch, and uses this data to calculate the distance by which a pitch misses its intended location. By combining each of these evaluations, STATS can determine the value of each pitch thrown.

In the charts throughout this article, each metric is shown both for specific pitchers in total and on a pitch-type basis. When looking at pitchers, the Total Batters Faced (TBF) in 2018 will be shown to give a sense for the scale of sample size. When looking at a pitcher’s performance separated by STATS’ pitch type classifications, the sample size will instead by denoted by the number of times each type was thrown by that pitcher during the season (Count).

Best Command

Often lost in the obsession surrounding strikeouts is the importance of command to continued success. While command in and of itself does not guarantee success, there are still several pitchers atop this leaderboard who had success in 2018 due mostly to their command. Using STATS’ unique pitch intent data, Command+ is determined by measuring the accuracy of each pitch based on the distance by which a pitch misses its intended location. By this metric, a league-average pitcher would have a rating of 100, and a Command+ rating of 112 means a pitcher is 12% better than league average at hitting his spots.

Few of these names come as a surprise, especially at the top of the leaderboard. Hendricks is well known as a command specialist, an idea verified through the application of Command+. Command is a skill that is widely consistent across pitch types, as both the soft-tossers and the hardest of pitchers have a relatively narrow spread of Command+ values amongst their most commonly used pitches. Among the leaders in Command+, excellence is defined by consistency across their range of offerings.

Best at Generating Bad Decisions

Making hitters chase bad pitches and take good pitches is a mark of a nasty pitch. STATS’ Discipline- rating (Disc-) is a measurement of how frequently a batter makes a bad decision when considering if he should swing at a pitch. From the pitcher’s side, this measures how frequently batters he faced make the wrong decision. A bad decision is deciding to swing at a pitch that is frequently called a ball or failing to swing at a pitch typically called a strike.

The chart below shows the top starting pitchers (at least 100 batters faced) in terms of creating bad decisions. A Discipline- rating of 100 would be league average for a pitcher, while Patrick Corbin’s league-leading rating of 74 means that he was 26% better than league average in this area during 2018.

For Corbin, much of his success in this area came from the emphasis he placed on his slider. Among starting pitchers, his slider had the best rating under this metric as it was an absurd 53 percent better than league average. Corbin threw his slider over 1200 times, representing approximately 40 percent of his pitches thrown on the season. On the other hand, Kluber’s success came more from having a wide array of consistently above-average offerings. Every pitch in his repertoire was above average by Discipline-, headlined by his cutter and changeup.

Best at Generating Whiffs

Where inducing bad decisions is one component of a dominant pitch, creating whiffs is the other side of what is considered a nasty pitch. Like Discipline-, STATS’ Whiff+ rating is expressed on a scale with 100 being league average.

Unlike Discipline-, a Whiff+ rating over 100 is better where each value over 100 represents a percentage better than the average pitcher. For example, a Whiff+ rating of 150 means a pitcher is 50% better at generating whiffs than the league average. This leaderboard presents a list of pitchers at the top of their field, all big strikeout pitchers.

Not all whiffs are created equal when measuring the performance of a pitch. Where fastballs are the most commonly thrown pitch, they are also relatively rarely whiffed on. On the other hand, breaking balls are thrown less frequently but result in a swing and miss more often. By adjusting to league average for each type, STATS’ Whiff+ rating accounts for the ability of each of a pitcher’s offerings to get a swing and miss relative to other pitches of its type.

Unsurprisingly, breaking balls, and especially sliders, are among the most successful pitches for generating whiffs. However, the names at the top of this list are characterized by their ability to generate whiffs on multiple pitch types. Take two of the pitchers at the top of this list in Verlander and Scherzer for example. Each of them has four pitches that are above average in terms of generating whiffs and are extremely proficient with fastballs and sliders.

Best Contact Managers

The final component of xRVAA- is the ability to consistently generate bad contact on balls in play. By including Statcast batted ball numbers, defensive shifts, the horizontal spray angle at which the ball is hit, and the batter’s running speed, we reach BIP-. This stat evaluates the quality of contact the pitcher surrenders relative to league average, with values under 100 being better than league average.

Keep in mind that the more a pitcher limits contact, the less important managing the quality of that contact is. Demonstrating part of the interconnected nature of each of these components, a better Whiff+ rating would be more forgiving of a lower BIP- rating.