The Data Analytics and Data Science teams at Aimpoint Digital recently set out to analyze the umpire performance for the 2021 MLB season.
Background & Goals
- Umpire scorecards (best and worst performance by ‘% Bad Calls’) in situations that could impact the game outcome.
- Umpires ranked by deteriorating performance in situations that could impact the game outcome.
- 10 worst calls in situations that could impact the game outcome.
Definitions
We define high-leverage situations as when there are either:
- 2 outs and runners on 2nd or 3rd base
- 7th inning or later and score difference between sides is 0-3 runs
We define super high-leverage situations as when both of the following are met:
- 2 outs and runners on 2nd or 3rd base
- 7th inning or later and score difference between sides is 0-3 runs
We define bad calls as:
- A ball incorrectly called a strike (i.e., when the ball crossed the plate, it was outside the strike zone)
- A strike incorrectly called a ball (i.e., when the ball crossed the plate, it was inside the strike zone)
Data Processing
- In total, between 2021-01-01 and today, there were 709,851 pitched balls available in the pybaseball source for 2371 regular season matches.
- Nine pitches were lost as they did not contain either strike zone or ball at plate data.
- A total of 682,834 records, 340,309 of these were ‘ball,’ or ‘called_strike’ were analyzed.
- Of these, 97,614 are classified as high-leverage situations.
- Of these high-leverage pitches, 11,185 (11.5%) were bad calls.
- For visualization purposes only, the vertical position of the ball was normalized as though every strike zone was 15 inches to 41 inches above the plate.
2021 MLB Umpire Analysis
Umpire Scorecards
The 10 best and worst performing umpires in high-leverage situations. The following table shows both incorrect strike and ball calls:
Umpire Performance Change - Worst
This table highlights the 10 worst umpires when comparing performance in ‘Not High-Leverage’ and ‘High-Leverage’ situations.
This means their performance deteriorates in high-leverage situations.
Umpire Performance Change - Best
This table highlights the 10 best umpires when comparing performance in ‘Not High-Leverage’ and ‘High-Leverage’ situations.
This means their performance improves in high-leverage situations.
The 10 Worst Strike Calls of the 2021 MLB Season
This visual shows the 10 worst strike calls of the 2021 MLB Season.
All incorrect calls in high-leverage situations are displayed in grey for context.
10 Worst Strike Calls in Super High Leverage Situations
This visual shows the 10 worst strike calls of the 2021 MLB Season in super high-leverage situations. We define super high-leverage situations as meeting the following criteria:
- 2 outs and runners on 2nd or 3rd base
- 7th inning or later and score difference between sides is 0-3 runs
All incorrect calls in super high-leverage situations are displayed in grey for context.
The 10 Worst Strikeout Calls of the 2021 MLB Season
This visual shows the 10 worst strikeout calls of the 2021 MLB Season.
All incorrect calls in high-leverage situations with 2 strikes are displayed in grey for context.
10 Worst Strikeout Calls in Super High Leverage Situations
This visual shows the 10 worst strikeout calls of the 2021 MLB Season in super high-leverage situations. We define super high-leverage situations as meeting the following criteria:
- 2 outs and runners on 2nd or 3rd base
- 7th inning or later and score difference between sides is 0-3 runs
All incorrect calls in super high-leverage situations with 2 strikes are displayed in grey for context.
10 Worst Ball Calls of the 2021 MLB Season
This visual shows the 10 worst ball calls of the 2021 MLB Season.
All incorrect calls in high-leverage situations are displayed in grey for context.
The 10 Worst Ball Calls with 2 Strikes of the 2021 MLB Season
This visual shows the 10 worst ball calls with two strikes of the 2021 MLB Season.
All incorrect calls in high-leverage situations with 2 strikes are displayed in grey for context.
Data Sources
Pybaseball
- Used to determine the strike zone, bad calls, and high-leverage situations, and all other information except the umpire for each game.
- https://github.com/jldbc/pybaseball
- https://jamesrledoux.com/projects/open-source/introducing-pybaseball/
Umpscorecards
- Used to determine the umpire for each game.
- https://umpscorecards.com/site-data/games.html
Technologies Used
Alteryx
- For a free trial of Alteryx click here
Tableau
