Getting Inside the Manager's Head

Do you ever watch a game and think that the manager is making a boneheaded decision by leaving a pitcher in or taking a pitcher out of a game? It turns out that the manager's 'gut' feeling can be quantified. In fact through the miracles of regression analysis, knowledge of baseball, and critical thinking, fans can now understand when and why a starting pitcher is going to be taken out of a game.

Joe Girardi Calling to the Bullpen

Using several continuous and categorical variables the number of pitches, age of the pitcher, runs allowed, and whether the game is being played at home and away had the most effect on the manager's decision to pull out a pitcher. We use these variables to predict innings pitched.

There is to be a note on runs allowed. If a pitcher is starting an inning and allows a base runner that base runner is to be considered a potential run until he is not on base. So when calculating how many innings a pitcher will pitch you are to include the runners on base on base in the current inning as runs. This is because often a manager's decision to take out a pitcher is based on the possibility of giving up more runs, also known as base runners.

In the regression equation, runs allowed has the greatest impact on whether a manager will take out the pitcher, which makes plenty of sense. It conveniently works out that each run allowed results in a deduction of one third of an inning pitched. Pitch count also has a lot to do when a pitcher is going to come out of a game. The more pitches a pitcher throws, the further he will go into a game, but not necessarily will be taken out.

An interesting thing I discovered when running this regression model was that 0.5 more innings are pitched by starting pitchers at home than away. People may say that makes plenty of sense because in order to conclude a win at home the home team has to pitch the top of the ninth but the away team does not have to pitch the bottom of the ninth. Managerial tendencies in today's game show that it is unlikely for a starting pitcher to pitch a complete game, so the extra half an inning does not have much to do with the concept of last licks, but rather strictly being at home.

Regression Equation:

A          Innings = 1.57 + 0.04734 Pitches - 0.3219 Runs + 0.0226 Age

H          Innings = 2.07 + 0.04734 Pitches - 0.3219 Runs + 0.0226 Age

Clayton Kershaw handing the ball over to manager
Don Mattingly 

The older the pitcher the further he is to go into the game, either due to experience or the manager's respect for the pitcher.

This equation is to be used a game goes on, because with each pitch the pitcher pitches the further he will go into the game. 100 pitches results in about 6 innings pitched without giving up a run. 100 pitches and 3 runs allowed results in about 5 innings pitched.

If a pitcher is approaching the inning which the equation yields he becomes more and more likely to get pulled from the game. If a pitcher pitches past the inning which the equation yields he becomes very likely to be taken out of the game. The regression model summary had a R^2 value of 65.38%. This means that 65.38% of the manager's decision to take a pitcher out of a game is attributed to these factors. Other non quantifiable factors that may effect a managers decision to take out a pitcher are a reliable bullpen, injury history, outliers in score, game delays, and ejections.

One variable that I tested that turned out not to have much effect on when a manager would take a pitcher out of a game was the categorical variable of League. Pitchers pitching in National League games stay in games to similar lengths as pitchers pitching in American League games.


 

Top 25 Starting Pitchers for 2014

Zack Greinke 

The following list is composed of the top 25 starting pitchers for the 2014 season. After each player's name is their current team and their ERA+ for the 2013 season. ERA+ is a statistic that compares a player's ERA to league average and is adjusted to home ball park. Previous seasons and consistency are considered in the ranking. There are several players that deserve to be on the list statistically but will need to prove themselves in the upcoming seasons.

1. Clayton Kershaw - Los Angeles Dodgers         194 ERA+
2. Felix Hernandez - Seattle Mariners                   121 ERA+
3. David Price - Tampa Bay Rays                        114 ERA+
4. Madison Bumgarner - San Francisco Giants      120 ERA+
5. Zack Greinke - Los Angeles Dodgers               135 ERA+
6. Yu Darvish - Texas Rangers                            145 ERA+
7. Justin Verlander - Detroit Tigers                      121 ERA+
8. Adam Wainwright - St. Louis Cardinals            123 ERA+
9. Jered Weaver - Los Angeles Angels                  115 ERA+
10. Stephan Strasburg - Washington Nationals      126 ERA+
11. James Shields - Kansas City Royals                131 ERA+
12. Chris Sale - Chicago White Sox                      140 ERA+
13. Cole Hamels - Philadelphia Phillies                   106 ERA+
14. Max Scherzer -   Detroit Tigers                      145 ERA+
15. Shelby Miller - St. Louis Cardinals                   119 ERA+
16. Jose Fernandez - Miami Marlins                      176 ERA+
17. Hisashi Iwakuma - Seattle Mariners                 138 ERA+
18. Gio Gonzalez - Washington Nationals              113 ERA+
19. Anibal Sanchez - Detroit Tigers                       163 ERA+
20. CC Sabathia - New York Yankees                   85 ERA+
21. Mike Minor - Atlanta Braves                           120 ERA+
22. Matt Latos - Cincinnati Reds                           121 ERA+
23. Jordan Zimmerman - Washington Nationals       116 ERA+
24. Hiroki Kuroda - New York Yankees                  122 ERA+
25. Garret Cole - Pittsburgh Pirates                        109 ERA+