1. Evaluating Intentional Walk Rule Change 2016-2017
Collin Kannenberg, Ben Stockton, and Brandon Allen
Mentor: Khyam Paneru, Ph. D.
Department of Mathematics, University of Wisconsin-Whitewater
Introduction
Velocity
First Pitch Balls/Strikes
First Pitch Balls/Strikes Cont.
In 2016 MLB instituted a rule change in regards to intentional walks. The manager of a team can now just signal to the umpire when they want the batter intentionally put on first base instead of the previous process of the pitcher lobbing four pitches to the catcher. In the previous century of baseball, very rarely did the batter actually get a hit off of an intentional walk nor did any other extraordinary event ever occur. The process of the intentional walk was changed as an effort to speed up the game. MLB Commissioner Rob Manfred issued this statement following this rule change, “We don’t think that that particular change — we know how the math works — is going to have a momentous impact on the game. By the same token, every little change that makes the game faster, I personally believe is a good thing for the game over the long haul (sun sentinel).” Some aspects of the game, however, may have been effected as a result of this rule change. By observing data from the two seasons, there are some results that could indicate the rule change having a more major effect on the game than just speeding it up.
Movement
The table contains the results of the t-tests comparing vertical movement in each of the pitches. Only vertical movement showed significant differences in a couple of pitches. There was no significant differenced in any pitches in regards to horizontal movement. From the results there is a significant difference in fastball horizontal movement from 2016 to 2017 and also the residual in The fastball had more movement in 2017 than in In 2017 compared to the average fastball movement, the pitches following the intentional walk had significantly more horizontal movement.
As observed from a full season ball/strike data following the intentional walk, we see similarly that 2017 has a high zone percentage compared to This can be take seriously because the zone percentage in total over the course of the seasons do not vary. This can be observed on in individual level to make it easier to see. For example:
This plot shows pitches after an intentional walk on August 21, Here are the rest of the same pitch type that they threw the rest of the game:
Average velocity of pitches thrown in 2017 and 2017
In sample, there is a significant change in first pitch strike percentage from 2016 to 2017 (p= ). In 2016 pitchers threw a first pitch strike following an intentional walk 57% of the time compared to 2017 when pitchers threw a first pitch strike 67% of the time.
Data
The data for this project was collected in multiple ways. One set of data is a sample of 555 plate appearances following the intentional walk. Half of the data is from 2016 and half from Plate appearances were randomly selected and the metrics were collected from the PitchRx database through R. From the pitchers’ data, their season averages were also put into the data set for comparisons. Another data set scraped from PitchRx contained full season data for both seasons which focused on the plate appearances following the intentional walk.
The table contains the results of the t-tests comparing the velocity separated by pitch type of the pitch following the intentional walk. There was a significant difference in the residual fastball velocity in for the fastball and the slider. In 2017, however no such significance is shown in any pitch.
Background on Intentional Walks
This is only three examples of what could be hundreds more. In a small sample it is easy to distinguish how pitchers can be observed throwing the first pitch following the intentional walk in a location different than they have been the rest of the game.
Conclusion:
Intentional walks may have shortened the game by a little bit, but was it worth the impact on the game itself. First pitches are an important part of the game for pitchers. In 2017 where the pitcher can keep his rhythm more, they tend to throw more first pitch strikes. Considering that most intentional walks occur in the late innings of games, this can sway the advantage towards the defense. Overall, although the evidence suggests greater first pitch strikes, over the course of the season this will not translate to all that many outs.
References:
The plot illustrates that most intentional walks occur in the late innings. These late innings contain more of the high leverage situations where the game is on the line. Intentional walks are then used to put the defense in a more advantageous position to get more outs without benefitting the offense significantly.
Baseballsavant.mlb.com
Baseballprospectus.com
Fangraphs.com
PitchRX