What is ZEF?
A singular metric to measure pitching effectiveness by zones
Introduction
About us
Jason Rollison (Twitter: @pbcbreakdown) is the founder and editor of Pirates Breakdown, one of the thought leaders in independent media covering the Pittsburgh Pirates. He also contributes to Beyond the Box Score and several daily newspapers. Jason lives in Bellefonte, PA with his wife
Jeremy Wyne (Twitter: @WaynoTexino) has been a baseball fan since listening to games on the radio with his great-grandmother as a preschooler. Using data to explain and better understand the game has always been of interest to him. He is an alumnus of Penn State and Carnegie Mellon Universities. Jeremy works as a software engineer in the South Hills of Pittsburgh where he resides with his wife and son.
Motivation
ZEF began as a research topic at Pirates Breakdown, an independent media outlet covering the Pittsburgh Pirates.
It was spurned on by Pirates pitching coach Ray Searage’s pre-season comment that the team would explore pitching higher in the zone. The fact that this would be an area of focus came as a surprise, as the Pirates are well known for focusing their pitching efforts towards inducing ground balls — thus utilizing the lower half/third of the strike zone intensely.
In order to intelligently comment on this, PBD founder and journalist Jason Rollison found it cumbersome to rely on so many different metrics to distill the particular effectiveness of using this area of the strike zone. He began to wonder if there was a way to roll up several metrics into one universal way to measure effectiveness by strike zone.
With the essential help of your presenter, Jeremy Wyne, we believe we may have found a way to do just that.
ZEF Defined
Methodology
Exit Velocity
Exit Velocity
- Exit Velocity (EV) is defined as the speed of a baseball after it is hit by a batter. This includes all Batted Ball Events (outs, hits, and errors)
- Low EV = weak contact = good for pitchers. Duh.
- Normalized score with league average = 0
Whiff%
Whiff%
- Whiff% is the percentage of the time the batter misses the ball when he swings
- High Whiff% = Missing Bats = good for pitchers. Duh.
- Normalized score with league average = 0
Deception Factor (DF)
Deception Factor (DF)
- Deception Factor (DF) is defined as Called Strikes / Total Takes
- or, "The ability of a pitcher to make a batter take a strike"
- High DF = deceptive = good for pitchers. Duh.
- Normalized score with league average = 0
Weights / Coefficients
Weights / Coefficients
- Least Squares Regression to error of ZEF as a predictor of fWAR*
- Calculated using all data season from 2015 to 2017 ASB**
* fWAR data from FANGRAPHS
** data from Statcast
Findings
Findings
As our initial resarch was focused around the Pirates, we will use them as a sample case study
Team Pitching WAR and ZEF
What you will next see is a three-year look at the Pirates' ZEF (all zones) as it relates to their pitching WAR, with individual component scores highlighted
ZEF and WAR
ZEF and WAR
ZEF and WAR
Takeaways
- These were oveall WAR and Effectiveness metrics (no zone splits)
- Demonstrated trendlines with positive correlation between ZEF and WAR
- Good pitching teams have high ZEF and WAR. Duh.
Team ZEF
and Zone Utilization
Pirates U3 zone utilization has increased each year from 2015 through the 2017 ASB
ZEF and WAR
ZEF and WAR
Takeaways
- After pitching to the upper third less often than all teams except for the Diamondbacks in both 2015 and 2016 the Pirates have utilized U3 over 10% of the time this season ranking them near the middle of MLB
- Since 2016 the Red Sox have led the way in frequency of pitching to U3
- Since at latest 2015 the Dodgers have dominated the league in effectiveness in the upper third of the zone
Pitcher
ZEF
The Pirates have recently targeted acquiring pitchers adept at utilizing the upper third of the strike zone, lending creedence to Searage's pre-season comments
The Pirates acquired Felipe Rivero via trade at the 2016 deadline.
The Pirates acquired Daniel Hudson via free agency before the 2017 season.
Other notable Pirates pitchers in the Upper Third of the Strikezone
Takeaways
- With the exception of Derek Holland, each acquistion target performed better than MLB average in the upper third of the zone every year since 2015
- The two pitchers acquired by the Pirates were at or near the top of MLB rank in U3 ZEF the season prior to acquisition (2015 Rivero & 2016 Hudson)
- Taillon, Cole, and Watson all actually reduced their U3 utilization from 2016 to 2017 while also improving their U3 ZEF
Team Zone Utilization
and Defense
As has been the case for some time, teams - especially the Pirates - are aligning pitching strategies with their defensive strengths to achieve run prevention synergies.
Batted Ball Type by Zone
MLB Avg 2015 - 2017
Defensive Metrics for BOS and PIT OF
Takeaways
- The Red Sox and Rays had oustanding outfield defenses in 2016 and they both pitched to the upper third more than all other teams
- Their BAA was significantly lower than what you would expect based on Avg Exit Velocity of balls put into play
- The 2016 Pirates outfield was quite poor defensively and BAA was high on pitches in U3 despite allowing the second lowest Avg EV
Conclusion
Future Work
- Batter ZEF
- Inside / Outside Zone Analysis
- Do we have the right components?
- Launch Angle?
- Pitch Type analysis (in progress)
- Quality of Contact? / Barrels?
- Spin Rate?
- Deception Factor refinement?
- Umpire Bias?
- Catcher Framing?
- Pitch Sequencing?
- Quantify Run Prevention Synergies
Thank you!
- Acknowledgements
- Fangraphs
- Statcast
- Pittsburgh Tribune-Review Pirates beat Rob Biertempfel (original Searage source quote)
- Dan Brooks and the entire team at Saber Seminar - THANK YOU!
Play along with the "home game" at
ZEFBASEBALL.COM
This presentation and all assorted materials will be presented at zefbaseball.com
Future Work
- Batter ZEF
- Do we have the right components?
- Launch Angle?
- GB/LD/FB?
- Quality of Contact? / Barrels?
- Spin Rate?
- What is DF?
- Umpire Bias?
- Catcher Framing?
- Pitch Sequencing?
- Quantify Run Prevention Synergies
There you will find:
- Interactive visualizations for ZEF at a team and player level
- Ongoing case studies
- A thorough, in-depth look at our formula
- COMPLETE publicly accessible Excel sheets with raw data
- & more!
Also please visit piratesbreakdown.com for more in-depth Pirates coverage!