The Maddux Plate Discipline Index (mPDI) for Hitters

Last week, I quantified a famous quote by Hall of Fame pitcher, Greg Maddux. He preached that the key to pitching is to throw a strike when the batter isn’t going to swing, and to throw a ball when the batter will [swing].

The introductory article to wPDI, the Weighted Plate Discipline Index for pitchers, can be found here.

Today, let’s turn the tables around and jump into the hitting equivalent. We can enumerate the offensive parallel of the quote – and evaluate what would be the “Maddux keys to hitting.” A Maddux hitter would swing at pitches when they are thrown in the zone and would lay off of pitches thrown out of the zone.

We will use the wPDI framework to help us quantify what we will call a “Maddux hitter.” For the hitting version of mPDI – the weights of the outcomes will be the exact inverses of the pitching indexes.

Again, here is a quick glossary of what the six possible plate discipline outcomes look like:

Classifying the 6 Hitting Outcomes
Outcome Outcome Outcome Outcome Outcome Outcome
A B C D E F
Zone? Out of Zone Out of Zone Out of Zone In Zone In Zone In Zone
Swing? Swung On Swung On No Swing Swung On Swung On No Swing
Contact? No Contact Contact Made No Swing No Contact Contact Made No Swing

Maddux Plate Discipline Index (mPDI) for Hitters:

The formula for mPDI, the Maddux Plate Discipline Index:

mPDI = IndexA * A% + IndexB * B% + IndexC * C% + IndexD * D% + IndexE * E% + IndexF * F%

A%, B%, …, F% is defined exactly as in wPDI – the percentage of total pitches per each outcome.

The mPDI indexes for hitters are given as:

Hitting Outcome Indexes for mPDI
Outcome Description Index
A Out of Zone / Swung On / No Contact 0%
B Out of Zone / Swung On / Contact Made 0%
C Out of Zone / No Swing 100%
D In Zone / Swung On / No Contact 100%
E In Zone / Swung On / Contact Made 100%
F In Zone / No Swing 0%

Since the indexes for C, D, E are all 100%, with A, B, F% all set to 0% – we can simplify the Maddux Plate Discipline Index (mPDI) for hitters as:

mPDI = C% + D% + E%

This represents the total percentage of outcomes where the batter swings at a pitch in the zone [Outcomes D & E] or looks at a pitch thrown outside of the zone [Outcome C]. We obviously know that hitting is far more complicated – but these are the outcomes for which hitters demonstrate plate discipline as alluded to by Greg Maddux. I will refer to outcomes C, D & E as the Maddux hitter outcomes [A, B & F – would be the Maddux pitcher outcomes].

mPDI for hitters tops out at just under .800 for the elite, and bottoms out just under .600. The average for mPDI for hitters is approximately .680.

Below are the 2018 leaderboards for mPDI (min 100 PA):

2018 mPDI for Hitters – Leaderboard
Name PA mPDI
Joey Votto 623 0.769
Matt Joyce 246 0.767
Corey Seager 115 0.762
Chris Iannetta 360 0.751
Luke Voit 161 0.751
Khris Davis 654 0.748
Guillermo Heredia 337 0.747
Yandy Diaz 120 0.747
Bryce Harper 695 0.745
David Freitas 106 0.744
Jed Lowrie 680 0.743
Jordan Luplow 103 0.742
Mark Reynolds 235 0.741
Chance Sisco 184 0.740
Brandon Belt 456 0.740
Russell Martin 352 0.739
Raffy Lopez 117 0.738
Kole Calhoun 552 0.737
Freddie Freeman 707 0.737
Tyler Flowers 296 0.736
Aaron Hicks 581 0.734
Robbie Grossman 465 0.734
Rosell Herrera 302 0.734
Brandon Lowe 148 0.733
Chris Taylor 604 0.733
Preston Tucker 184 0.733
Ryan Flaherty 182 0.732
Alex Avila 234 0.732
Steve Pearce 251 0.731
Roman Quinn 143 0.730
Andrew McCutchen 682 0.730
Jeff McNeil 248 0.729
Craig Gentry 169 0.729
Brandon Nimmo 535 0.729
Ryan O’Hearn 170 0.728
Eric Young Jr. 117 0.728
Alex Blandino 147 0.728
Steven Souza Jr. 272 0.728
Jorge Bonifacio 270 0.727
Leonys Martin 353 0.727
Daniel Descalso 423 0.726
Matt Olson 660 0.726
Ronald Acuna Jr. 487 0.726
Mitch Moreland 459 0.726
Hanley Ramirez 195 0.724
Jesse Winker 334 0.724
Joe Panik 392 0.724
Ian Happ 462 0.724
Eugenio Suarez 606 0.724
Colin Moran 465 0.724
Andrew Knapp 215 0.723
Enrique Hernandez 462 0.723
Scott Schebler 430 0.722
Jay Bruce 361 0.722
Minimum 100 PA

Joey Votto is the king! I can’t say that I am the least bit surprised. Votto currently owns an amazing career .310 BA and .426 OBP. His plate discipline skills are one of the best of all time. Votto excels in Outcome C – Not swinging at pitches outside of the zone.

In fact, let’s take a peek at the leaders specifically in Outcome C for 2018:

Name PA Outcome C Component mPDI
Daniel Vogelbach 102 0.479 0.713
Russell Martin 352 0.476 0.739
Jose Ramirez 698 0.463 0.715
Joey Votto 623 0.462 0.769
Alex Bregman 705 0.462 0.718
Jose Bautista 399 0.461 0.711
Mookie Betts 614 0.460 0.703
Aaron Hicks 581 0.459 0.734
Alex Avila 234 0.459 0.732
Aaron Judge 498 0.455 0.705
Alex Blandino 147 0.452 0.728
Jake Bauers 388 0.451 0.709
Max Muncy 481 0.451 0.697
Mike Trout 608 0.450 0.701
Justin Smoak 594 0.450 0.706
Bryce Harper 695 0.450 0.745
Josh Donaldson 219 0.447 0.719
Ji-Man Choi 221 0.446 0.719
Brandon Nimmo 535 0.446 0.729
Robbie Grossman 465 0.445 0.734
Matt Carpenter 677 0.445 0.697
Ryan O’Hearn 170 0.445 0.728
Francisco Cervelli 404 0.444 0.717
Steve Pearce 251 0.444 0.731
Daniel Robertson 340 0.444 0.683
Kyle Schwarber 510 0.444 0.708
Josh Bell 583 0.443 0.711
Carlos Santana 679 0.443 0.715
Minimum 100 PA

Votto finishes as the 4th best player in the above. Towards the top of this list, we can find a number of elite batters such as Jose Ramirez, Alex Bregman & Mookie Betts.

Daniel Vogelbach leads all batters in Outcome C with a component of .479 (.713 total mPDI). Vogelbach posted a 13% walk rate last season in 102 plate appearances. To date in 2019, he has increased his BB% to 15%. Walk rate & strikeout rate (plate discipline skills) are among the first quantities to stabilize. Dan may be headed for another great season as far as plate patience goes, and he is finally getting some playing time.

Other notable players that catch my eye here are Robbie Grossman, Ryan O’Hearn and Josh Bell. Monitor the trio for their batter’s eye in 2019. Bell already has started off the season well, rebounding from a disappointing sophomore season in ’18. To date in 2019, Bell’s mPDI has surged to .782, which is elite territory.

Below are the top Outcome E batters for 2018:

Name PA Outcome E Component mPDI
Jeff McNeil 248 0.323 0.729
Noel Cuevas 153 0.315 0.670
Corey Seager 115 0.308 0.762
Nick Hundley 305 0.308 0.708
Aledmys Diaz 452 0.307 0.687
Daniel Murphy 351 0.303 0.681
Colin Moran 465 0.300 0.724
Kurt Suzuki 388 0.299 0.679
Freddie Freeman 707 0.298 0.737
Mason Williams 132 0.296 0.691
Yandy Diaz 120 0.296 0.747
Anthony Rendon 597 0.295 0.706
Ozzie Albies 684 0.293 0.702
Joe Panik 392 0.293 0.724
Jose Fernandez 123 0.292 0.672
Jesus Sucre 198 0.292 0.633
Ender Inciarte 660 0.291 0.699
Dee Gordon 588 0.290 0.631
David Freitas 106 0.289 0.744
Hanley Ramirez 195 0.288 0.724
Starling Marte 606 0.288 0.696
Howie Kendrick 160 0.287 0.644
Minimum 100 PA

Outcome E quantifies the percentage of all pitches for which the batter swung at a pitch in the zone and made contact. We see elite names at the top of this list such as Freddie Freeman, Corey Seager and Anthony Rendon.

Most notably atop the Outcome E leaderboard is utility man Jeff McNeil (.729 mPDI). Jeff posted a .329 BA in 248 plate appearances last season. To date in ’19, McNeil is hitting at a .383 clip, so he has continued his torrid contact skills. Outcome E represents the contact component of the Maddux plate discipline categories (Outcome C embodies a good eye). McNeil has a 10% strikeout rate for his career.

To close, let’s take a look at the lowest mPDI hitters from 2018:

2018 mPDI for Hitters – Bottom Leaderboard
Name PA mPDI
Chase d’Arnaud 100 0.594
Magneuris Sierra 156 0.598
Francisco Pena 142 0.609
Jose Iglesias 464 0.610
Hernan Perez 334 0.613
Kevin Pillar 542 0.613
Austin Wynns 118 0.614
Pablo Sandoval 252 0.617
Victor Reyes 219 0.618
Francisco Arcia 106 0.620
Carlos Tocci 135 0.621
Dawel Lugo 101 0.621
Scott Kingery 484 0.624
Jesus Aguilar 566 0.627
Dee Gordon 588 0.631
Ronny Rodriguez 206 0.632
Charlie Tilson 121 0.633
David Fletcher 307 0.633
Jesus Sucre 198 0.633
Javier Baez 645 0.634
Albert Almora Jr. 479 0.635
Joey Wendle 545 0.635
Amed Rosario 592 0.636
Jose Briceno 128 0.638
Ryon Healy 524 0.639
Odubel Herrera 597 0.639
Jose Abreu 553 0.641
JB Shuck 142 0.641
Jonathan Lucroy 454 0.642
Andrew Romine 131 0.642
Dominic Smith 149 0.643
Albert Pujols 498 0.644
Minimum 100 PA

The bottom of the mPDI boards represent the wild swingers, and the hitters who let good pitches go by.

Salvador Perez (.590 mPDI) swings at a ton of pitches outside the zone. 63% of the pitches that he sees is out of the zone, and about half of those (30% of total pitches) are swung at. In standard plate discipline terms, he has a large O-Swing%. He happens to make contact in almost two-thirds of the out-of-zone pitches, but he is swinging at far too many bad pitches. Unfortunately, Perez is injured and will be out for the rest of the 2019 season.

Jose Iglesias (.610 mPDI) lurks at the bottom of mPDI not for his wild swinging, but rather, for his non-swinging. Over 17% pitches that Iglesias sees are thrown in the zone and not swung at. He had a miniscule walk rate of 4% in 2018 in 464 plate appearances. Iglesias looks quite a bit different in ’19 – as he upped his BB% to 11% thus far, albeit with a 20% K%. It is clear that he is swinging more often than he has in the past. This may be the result of his change in teams (to the Reds), and/or working with a different hitting coach. To date, his mPDI is still below league average, but is improved at .643.

Once again, hitting is not as simplistic as Greg Maddux implied (by the inverse of his pitching key). However, this is a great place to search for players who exhibit excellent plate discipline skills, which typically translate well from year to year. Players with a high mPDI who are due for an increase in playing time this season – are candidates to breakout or may simply post a superb on-base percentage.

Ariel is the 2019 FSWA Baseball Writer of the Year. Ariel is also the winner of the 2020 FSWA Baseball Article of the Year award. He is the creator of the ATC (Average Total Cost) Projection System. Ariel was ranked by FantasyPros as the #1 fantasy baseball expert in 2019. His ATC Projections were ranked as the #1 most accurate projection system over the past three years (2019-2021). Ariel also writes for CBS Sports, SportsLine, RotoBaller, and is the host of the Beat the Shift Podcast (@Beat_Shift_Pod). Ariel is a member of the inaugural Tout Wars Draft & Hold league, a member of the inaugural Mixed LABR Auction league and plays high stakes contests in the NFBC. Ariel is the 2020 Tout Wars Head to Head League Champion. Ariel Cohen is a fellow of the Casualty Actuarial Society (CAS) and the Society of Actuaries (SOA). He is a Vice President of Risk Management for a large international insurance and reinsurance company. Follow Ariel on Twitter at @ATCNY.