RADIO
Ariel Cohen reviews his wPDI (Weighted Plate Discipline Index) leaderboard for the early portion of the 2021 MLB season to find undervalued hitters for fantasy baseball.
In 2019, I introduced a new (yet simple) statistical metric which focuses on the core ingredients of plate discipline. The Weighted Plate Discipline Index (wPDI) looks at the following basic binary events:
- Was the ball thrown in the zone?
- Was the ball swung on?
- Did the batter make contact with the ball?
Weighted Plate Discipline Index (wPDI) does not look at exit velocity, barrels, or quality of contact. It doesn’t look at walk rates or strikeout rates, or at any other plate appearance result.
wPDI focuses solely on pitches. Is the pitch in the zone? Did the batter swing at the pitch? Did the hitter contact the pitch? That’s all.
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wPDI Matrix
By answering the three binary questions above, each and every pitch can be classified into one of the following tracked six outcomes.
| Outcome A | Outcome B | Outcome C | Outcome D | Outcome E | Outcome 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 |
Each plate discipline outcome can be enumerated, and subsequently expressed as a percentage of all pitches thrown. By indexing each outcome appropriately, and by aggregating in linear fashion - wPDI can be used as an accurate representation of many other statistics (called strikes, whiffs, strikeouts, walks, etc.). wPDI can also find undervalued deceptive pitchers.
The Maddux Plate Discipline Index (mPDI), named after Hall of Fame pitcher Greg Maddux, is modeled after his famous quote about pitching:
“The key to pitching is to have the ability to throw a strike when they’re taking and throw a ball when the hitter is swinging.”
The Maddux Plate Discipline Index (mPDI) is a special case of wPDI. For pitchers, this would be represented by the following quantity:
Outcome A + Outcome B + Outcome F
Total Pitches
As for batters, we would need to consider the exact inverse of Maddux’s quote. The key to hitting would be to swing when the ball is in the zone, and to lay off when the ball is out of the zone. The Maddux Plate Discipline Index (mPDI) for hitters captures all of the other plate discipline scenarios. In terms of the six defined outcomes above, mPDI for hitters is defined as:
Outcome C + Outcome D + Outcome E
Total Pitches
Today’s article focuses on the mPDI leaderboard for hitters through May 4. An awful mPDI would be one in the upper .500s, while an elite one would approach .800. An mPDI of .685 is about average thus far for 2021.
Let’s now go through a few early Maddux Plate Discipline Index studs. We will dive into some of their underlying metrics in the early going of the season, as well as their specific plate discipline component outcomes.
mPDI Leaders
First, let’s take a look at the current mPDI leaderboard for 2021. Below are the top plate discipline batters with a minimum of 30 plate appearances:
Mike Tauchman, New York Yankees
After just 11 games played as a member of the crowded Yankees, Mike Tauchman was traded to the San Francisco Giants. With a career wRC+ of 101, Tauchman should have had a regular major league role, but was marginalized in New York. He offers a good defensive glove and a hint of speed.
But what jumps out in Mike's first 33 plate appearances of the season is his eye. Tauchman's .805 mPDI currently leads all of baseball. Looking into his Maddux Plate Discipline components - Tauchman has so far excelled in strike recognition.
| Player | mPDI | Outcome C Percentile | Outcome D Percentile | Outcome E Percentile |
| Mike Tauchman | .805 | 71% | 97% | 88% |
His in-zone plate discipline outcomes (Outcomes D & E) are elite. Almost 40% of all the pitches thrown to Tauchman are in the zone and are swung on. His called strike rate is less than 10%.
Tauchman hasn’t walked much thus far in 2021 (just 1 BB). But as his career walk rate is 12%, and was 13% last season, you should expect a rise from here on in.
The Giants have been splendid in April, and I envision Tauchman getting plenty of opportunity in the short term this May. If he continues to bat near the top of the lineup, he will also get a large boost in his run production counting stats – which is pertinent for your fantasy leagues. Keep an eye out on Tauchman.
Jordan Luplow, Cleveland Indians
Next on the mPDI list is Jordan Luplow.
| Player | mPDI | Outcome C Percentile | Outcome D Percentile | Outcome E Percentile |
| Jordan Luplow | .792 | 98% | 54% | 55% |
In terms of plate discipline, his strength is his “ball” detection. Nearly half of the pitches thrown to him are out of the zone and not swung on (an Outcome C of 49%). His walk rate this season is up over 16%, which is even higher than his 12% career average.
Heading into the season, Luplow was thought of as a platoon hitter. His lefty-righty splits are spread wide apart. His career wRC+ vs. left-handed pitching is a tremendous 154, whereas his wRC+ vs. RHP is just 64. This season, Jordan is even getting more consistent playing time. His 6 HRs are split evenly against right-handed and left-handed pitching.
Ignore Luplow’s low batting average to start the season of .183, which is largely BABIP aided. A BABIP of .135 is quite an unlucky mark. Otherwise, he is having his best season to date. In addition to the rise in his walk rate (mentioned above), he is barreling balls at the highest rate of his career (16%), his exit velocity is up 2 MPH from his norm, and his run production per plate appearance has risen to new heights.
As long as Luplow continues to get playing time, and especially if Cleveland continues to bat him in the two-hole, he will be fantasy relevant. Continue to monitor this Maddux Plate Discipline stud. Scoop him up off the waiver wire in moderate to deep leagues.
Brandon Belt, San Francisco Giants
Brandon Belt is having a nice start to the 2021 season, with six HR and 18 RBI. Despite a career-high strikeout rate (33%), mPDI believes that Belt has been a plate discipline stud. At .777, Belt’s mPDI is ranked fourth in the major leagues.
| Player | mPDI | Outcome C Percentile | Outcome D Percentile | Outcome E Percentile |
| Brandon Belt | .777 | 94% | 72% | 64% |
Belt not only excels in out-of-zone recognition (Outcome C), but he also identifies strikes well (Outcomes D & E). He is superb across the board in all of the Maddux Plate Discipline categories, with an elite eye for "balls."
Aside from an excellent 16% walk rate to start 2021, Belt is barreling balls at a 20%+ clip – which has boosted his hard-hit rate over 50%.
Throughout his career, Brandon seems to perform well early on in the season. His 137 career wRC+ in the month of May is the best of his monthly splits. His career batting average in May is a robust .274. Now would be the optimal time to get Belt into your lineups, and while he is still healthy.
Chris Taylor, Los Angeles Dodgers
With a .766 mPDI, Chris Taylor of the Dodgers has been a top 10 Maddux Plate Discipline player. His walk rate has risen to the highest level of his career at 14%, while his strikeout rate has dwindled to its lowest point at 23%. His mPDI plate discipline profile looks similar to that of Jordan Luplow.
| Player | mPDI | Outcome C Percentile | Outcome D Percentile | Outcome E Percentile |
| Chris Taylor | .766 | 92% | 56% | 69% |
Looking at Taylor’s Statcast metrics, his exit velocity is sitting 4 MPH above his career average and he is barreling balls at a 12.5% clip (1 out of every 8 events). In 2021, he has produced an xwOBA of .401, confirming his early success.
From a rotisserie perspective, he has more than exceeded his fantasy managers' expectations. The Razzball player rater currently ranks Taylor as the 42nd best player in 5x5 roto - thanks to 24 runs, 4 HR, 3 SB, and a robust .267 BA.
Taylor has taken full advantage of near regular at-bats in the past few weeks. Consider rostering Taylor in shallow leagues, and trading for him in deeper leagues. The Dodgers will have a potent offense once again in 2021, and if he continues to bat high up in the lineup - Taylor could approach 90 runs and 75 RBI on the season.
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