Earlier this year, I looked at a few plate discipline standout hitters to monitor. These players were highlighted based on my new weighted index statistic for hitters - mPDI, which quantifies a simple concept alluded to by the great Greg Maddux. 

Swing at strikes, and don't swing at balls. 

The four hitters that I had highlighted (Josh Bell, Jeff McNeil, Luke Voit and Daniel Vogelbach) have not disappointed this year.
Let's check in to see who sits atop the Maddux Plate Discipline Index (mPDI) thus far in 2019.

2019 mPDI leaderboard (min. 40 PA)

Among players with at least 40 plate appearances, some familiar names appear towards the very top. Joey Votto (.749), despite having a down season – still ranks 10th among all hitters. Other stars such as Freedie Freeman, George Springer and Anthony Rendon also appear high up. Josh Bell and Luke Voit, whose mPDI highlighted last season – are now entrenched firmly as elite plate discipline hitters for the 2nd straight season.

Let's take a look at a few other players to take note of on the mPDI leaderboard:

2019 mPDI Leaderboard (min 40 PA):
Cavan Biggio770.792
George Springer2160.769
Chris Iannetta960.767
Victor Caratini710.764
Luke Voit3130.763
J.P. Crawford900.76
Jordan Luplow1340.756
Anthony Rendon2460.752
Andrew Knapp660.75
Joey Votto2780.749
Scott Schebler950.748
Kyle Seager1070.747
Ryan McMahon2010.747
Brandon Belt2580.747
Derek Fisher600.746
Sean Rodriguez510.745
J.D. Davis1870.744
Mike Tauchman1180.744
Freddie Freeman3310.744
Dexter Fowler2330.744
Mitch Moreland1740.743
Brad Miller420.742
Carlos Santana3060.741
Peter O'Brien470.741
Chad Pinder1740.739
Josh Bell3120.739
Christian Walker2780.739
Khris Davis2480.739
Kris Bryant3020.738
Yandy Diaz2480.738
Kole Calhoun2890.735
Michael Conforto2790.735
Tommy Pham2990.735
Robbie Grossman2230.734
Max Kepler2900.734

Cavan Biggio (.792 mPDI)

Rookie Cavan Biggio leads all players in mPDI this season (with at least 40 plate appearances). He has accumulated a very interesting line thus far, slashing .212/.358/.470 with 5 HRs in his first 66 ABs [81 PA]. He has walked 15 times, for an incredible walk rate of 19%, so his batting eye is quite keen here in the embryo stage of his career.

His batting average will surely come up from .212. He has been quite unlucky thus far on balls in play with a .231 BABIP. His Hard-Hit contact rate is at 52%, so it is clear he is hitting the ball hard; the base hits will come for him. The power is already there with a HR/FB rate of 21%.

He was having a wonderful season in AAA prior to his callup, which led to his promotion. His OBP was nearly .450 in the minors this season! Biggio also has some legs, he stole 20 bases while in AA last season. He has already stolen two bases while up in the majors. There are many possible paths to Fantasy value for the son of a Hall of Famer.

In terms of plate discipline, it is Biggio's Outcome C that has propelled him to sit atop the mPDI leaderboard. Outcome C refers to "not swinging at pitches outside of the zone."

A quick refresher on the six plate discipline outcomes:

Outcome AOutcome BOutcome COutcome DOutcome EOutcome F
Zone?Out of ZoneOut of ZoneOut of ZoneIn ZoneIn ZoneIn Zone
Swing?Swung OnSwung OnNo SwingSwung OnSwung OnNo Swing
Contact?No ContactContact MadeNo SwingNo ContactContact MadeNo Swing

A full explanation of the definitions of the various plate discipline outcomes can be found here.

2019 Outcome C leaderboard (min. 40 PA)

NamePAmPDIOutcome COutcome DOutcome E
Cavan Biggio770.7920.5290.0480.214
Ben Zobrist990.7130.5030.0260.183
Mike Trout3120.7180.4850.0160.217
Mitch Garver1400.6970.4830.0250.189
Alex Avila780.7110.4810.0470.183
Carlos Santana3060.7410.4780.0360.227
Justin Smoak2610.7320.4780.0270.228
Alex Bregman3210.7270.4760.0220.229
Logan Forsythe1950.7080.4730.0330.203
Aaron Hicks1130.710.4680.0470.195
Roberto Perez1880.7230.4670.0560.199
Daniel Vogelbach2690.6730.4660.0380.168
Joey Gallo2140.7290.4660.070.193
Tommy Pham2990.7350.4650.0330.236

No one has held off of swinging outside of the zone (as a percentage of total pitches) more than Biggio has in 2019. He is currently ahead of coveted Mike Trout territory in this regard, which says quite a lot.

The Blue Jays have high hopes for Biggio, and you should take a good look at this plate discipline stud for your Fantasy rosters too.

Jordan Luplow (.756 mPDI)

Unlike Biggio, who excelled at one plate discipline outcome, Jordan Luplow is able to maintain a very high level in each of the Maddux plate discipline categories. In terms of his batted ball profile, Luplow has made some changes to his repertoire since last season. He is hitting more line drives, going less to the opposite field, and he is hitting barrels at a much higher rate than last year. Not to mention, but his HR/FB rate has nearly tripled since last season.

Luplow crushes left-handers. He has a .467 wOBA and a fantastic 1.158 OPS against southpaws. His batting average is a lofty .318 vs LH as opposed to a meager .190 against righties [.211 wOBA /.484 OPS vs RH].  That is an incredible split that is so divisive that Luplow regularly bats in the cleanup spot whenever the Indians face a left-handed pitcher. He is absent when they race a righty.

His value in Fantasy Baseball would come in leagues that allow for daily lineup changes -- i.e. in leagues that would allow one to platoon him. He may also be valuable in a DFS setting. In standard weekly leagues, you may only want to play him in deep leagues or for weeks when Cleveland faces an abundance of left-handed pitching.

The elite mPDI has called Luplow to my attention. I won't be rostering him in my lineup for the time being though, until I can count on him for more volume. On a per at-bat though, he has solid power metrics.

Max Kepler (.734 mPDI)

The Twins' Max Kepler is having an incredible season. Though we haven't even played half of 2019 yet, with 19 homers, Kepler is just one away from his career high of 20. He is on pace to hit over 40 round-trippers this year. Kepler is slashing a healthy .273/.355/.562, has scored 50 runs and also has knocked in 50 for the season.

In looking deeper into Kepler's plate discipline, we can see that it is Outcome E for which he excels.

2019 Outcome E leaderboard (min. 40 PA)

NamePAmPDIOutcome COutcome DOutcome E
Alen Hanson480.730.3040.0620.359
Willians Astudillo1210.670.3050.0110.349
Austin Romine1000.680.2970.0440.336
Jose Peraza2080.680.3560.0080.318
Dee Gordon2030.70.3540.030.312
Chad Pinder1740.740.3720.0560.311
Jeff McNeil2450.710.3650.0410.309
Adeiny Hechavarria850.690.3220.0610.307
Andrelton Simmons1950.690.3730.0130.306
Max Kepler2900.730.410.0210.303
Aledmys Diaz1090.680.3540.0210.301
Kevin Kiermaier2540.710.3640.040.301
Kurt Suzuki1370.690.350.0330.301

Outcome E enumerates the pitches that are thrown in the zone and which are contacted. Kepler isn't letting many good pitches go by this season. He is also hitting the ball harder than ever; he has increased his hard hit contact rate from 37% in '18 to 44% this season. 

I think that Kepler can sustain much of this lofty production for the duration of '19. Kepler has been able to cut down on his strikeouts. He has now lowered his strikeout rate in every season since his debut in 2015.

Kepler has also made a small change in his launch angle, from 16 degrees in '18 to 18 degrees this season. With that, his HR/FB rate has almost doubled from his 2018 levels.

A few other mPDI hitters to monitor

J.D. Davis (.744), Ryan McMahon (.747), Chad Pinder (.739)

Davis this year is showing strong Statcast metrics – with an average exit velocity of 91 MPH, and a max EV of 114.7 MPH. The average exit velocity ranks 60th among all hitters, and the max velocity ranks 25th in baseball. Showing superb plate discipline and having the ball fly off of the bat when contact is made is a wonderful combination.

McMahon, who calls Coors Field home is someone to keep a lookout for as well. He has compiled a .273 batting average for the season with a decent 11% walk rate. He is even better at home (.288 BA), and better against lefties (.345 BA). Given that, use him appropriately for advantageous matchups in your leagues.

Chad Pinder has shown excellent power in small pockets of playing time in his career. Last season, in just 298 ABs, he hit 13 HRs. Between 2017-2018 – in 580 ABs, he has amassed 28 home runs. He is hitting just .250 this season, but lately he has been cutting down on swings outside of the zone and has been swinging at more strikes. Monitor Pinder as a possible low-end power source.