From the perspective of a hitter digging into the box, every pitch initiates a critical split-second thought process that could impact the entire at-bat: to swing or not to swing.
Some websites dedicated to analytics traffic in metrics like a batter’s swing rate, often on pitches both in and out of the strike zone, in an effort to measure discipline. That’s not good enough. Not all decisions to swing or take are created equal.
For example, a batter protecting the plate with two strikes who swings at a pitch just out of the zone shouldn’t be penalized the same as a hitter whiffing on a pitch way off the plate on a 3-1 count.
Of course, deciding whether to take a hack is only the first component of an at-bat. The next is whether the batter makes contact, and finally, what he’s able to do with the ball if contact is made. Stats Perform now measures how much value a player adds to his offensive line in all three of those aspects, having developed what we believe are the only all-encompassing metrics for discipline (Discipline+), the ability to make contact (Contact+) and bat-on-ball impact (BIP+).
Here’s a closer look at each of those metrics, starting with the first component of an at-bat: to swing or not to swing.
As we wrote above, not every decision to swing is created equal.
Stats Perform differentiates them by assigning to every pitch a value based on velocity, movement, location, and count. From this, the hitter is given a value of his own based on his decision to swing or take said pitch. A batter gets more credit for swinging at a pitch that has a 90% chance of being called a strike than if he decides to cut loose on a pitch that has a lower probability.
So considering that the league average is 100, here’s who finished in the top 10 in Discipline+ in 2019 (minimum 500 plate appearances):
As expected, some of the game’s most patient hitters are in the top 10. But there are plenty of sluggers there too. Mike Trout worked a base on balls on a Major League-high 18.3% of his plate appearances and hit 45 home runs. Alex Bregman was third in walk rate (17.2) and belted 41 homers and Juan Soto was sixth (16.4) and had 34 dingers.
Improved discipline also played a major role in Marcus Semien’s emergence as an MVP candidate, as he finished with a .285 batting average, 33 home runs and 92 RBIs – all career highs. His walk rate has improved in each of the past four seasons and was a career-best 11.6 in 2019. Semien ended up third in the AL MVP voting, coincidentally behind Trout and Bregman.
After the batter has made that split-second decision to swing, Stats Perform can evaluate his ability to generate frequent contact like no one else. While some sites use advanced stats such as contact rate or contact percentage in and out of the strike zone, we’re able to use Discipline+ and Contact+ to conduct a more thorough analysis that can even determine which batters have elite hand-eye coordination.
To show how, we’ll need to examine how Contact+ works. Similar to Discipline+, we work with the velocity, movement, location, count and other factors of a pitch. But here we determine the probability of a league-average hitter making contact on each. If the league-average contact rate on the average pitch is around 75% and the batter makes contact on 80 out of 100 of those pitches, he’s 5% better than league average in Contact+. (This does not include foul-tips that land in the catcher’s glove)
It’s easy to see why Anthony Rendon is a nightmare for opposing pitchers. He’s the only player to rank in the top 10 in both Discipline+ and Contact+, meaning he rarely swings at stuff he can’t handle and often makes contact when he does.
Here is the rest of the game’s best at making frequent contact in 2019:
|4||Kevin Pillar||Blue Jays/Giants||114|
Players who often swing at pitches with a higher probability of generating weak contact are going to have a lower value in Contact+. There is often a negative correlation between Discipline+ and Contact+ because there are many patient hitters who also strike out a lot. Adam Dunn and Kyle Schwarber are good examples. But on the flip side are players we know to have elite hand-eye coordination because they swing at most everything yet still manage a solid Contact+ rate.
Hanser Alberto, Jose Iglesias and Kevin Pillar fall into this category, as they rank among the leaders in Contact+ despite having well below-average plate discipline. Alberto finished with a 61 in Discipline+, while Iglesias had a 65 and Pillar a 60.
The decision to swing has been made and the bat has met the ball. Now we can measure a batter’s impact once he’s put it in play.
BIP+ has a similar algorithm to Contact+, but here we set an expected outcome for each pitch (instead of a contact probability) by using some of the same factors previously mentioned. From there, we’re able to use the actual outcome’s launch angle, exit velocity, the player’s sprint speed, whether he was facing a defensive shift, the horizontal spray angle of the ball and more to give that outcome a value and compare it with the league-average ball in play.
As mentioned in our examination of Raw Value, which is essentially a cumulative measure of all three components dissected here, the horizontal spray angle is the left/center/right location of the ball. If a ball is hit at a 30-degree launch angle at 100 MPH toward one of the foul poles, it’s probably going to be a home run. If it’s hit to straightaway center, it’s much less likely to leave the ballpark. That’s something advanced metrics on other sites don’t take into account.
BIP+ is a more complete measure than the more mainstream batting average on balls in play (BABIP), as it accounts for the difficulty of hitting a particular pitch. Should a positive outcome off a grooved fastball on a 3-1 count have the same value as one that comes on a nasty 0-2 pitch? We don’t think so either.
Here were the top BIP+ performers in 2019:
|6||Ronald Acuna Jr.||Braves||182|
|7||J.D. Martinez||Red Sox||181|
Minnesota Twins slugger Nelson Cruz only played in 120 games in 2019, but he made the most of them with 41 home runs and a BIP+ that easily topped Trout’s and more than doubled the league average. Christian Yelich similarly put up huge numbers with a .329 average and 44 homers in just 130 contests.
It’s no surprise to see Jorge Soler, who led the AL with 48 home runs, and Pete Alonso, who paced MLB with a rookie-record 53 homers, on the list. Schwarber and Franmil Reyes had the lowest batting average in the top 10 at .250 and .249, respectively, revealing how much damage they do when they actually make contact. (Both are below the league average in Contact+.)
In an attempt to show how all three metrics fit together, let’s look at Chicago Cubs shortstop Javier Baez. The two-time All-Star has a well below league average Discipline+ of 58, which isn’t much of a surprise for anyone who has seen his at-bats. But his Contact+ rate is relatively high at 99 – just barely under the league average.
What does this mean?
Well, if Baez were to adjust his free-swinging approach and cut loose on the “right pitches” by our measure, his strikeout rate – 27.8% in 2019 – would move closer to the league average (an all-time high 23.0% in ’19). Fewer strikeouts would mean more balls in play, and given that his BIP+ is 164, he’d likely be even better than his .286 average, 63 home runs and 196 RBIs over the past two seasons.
Advanced analytics and data analysis provided by Lucas Haupt