Up until this point, all of my analysis for RotoFanatic has been focused on pitching. My StuffERA model and the underlying aspects of the model all have led me to focus my attention on pitching. However, as I teased in the introduction to StuffERA, the whole concept was actually built around hitting. My goal was to better understand the swing decisions that certain hitters make. Mainly, I wanted to develop a better tool for determining plate discipline.

As I mentioned in that first piece, I was able to create a generic plate discipline metric that factors in the quality of the pitches a given hitter sees. This helps me to determine the hitters who are truly elite at swinging at the right pitch, instead of those who are far too passive. Yet, in this entire process, I discovered the idea of Influence. Influence is what I call the individual player’s impact on an event. As you saw with pitchers, this could be their ability to generate extra whiffs or limit wOBACon. Today, I want to look at this through the lens of hitters and see who is Influencing Whiffs and wOBA the most in 2020.


Whiff Influence


As I stated in the initial article introducing StuffERA, not all whiffs are created equal. From a pitching standpoint, a Joey Gallo whiff is less impressive than a David Fletcher one. Similarly from a hitters perspective, Shane Bieber is more likely to get you to swing and miss than Mike Fiers. The idea behind the influence metrics is to entirely strip the opponent away and factor in just the hitter or pitcher themselves. This also factors in the location and expectation for a given pitch.

Let’s take two hypothetical hitters with a 15% whiff rate. Hitter A saw pitches with an underlying expected whiff rate of 15%, while Hitter B had an expectation of 10%. Assuming they only faced a league-average pitcher, this would mean Hitter A has a whiff influence of 0, and Hitter B has one that is 0.05 or 5%. In your eyes which hitter would you look at as more whiff prone? Obviously, you would look at Hitter B to be more whiff prone despite the two hitters having identical actual rates. This is the point of whiff influence. This is the same idea as what has been discussed with pitchers, however as you’ll see, hitters have a much greater impact on these results. The range of high end to low-end Influence for hitters is almost twice as large as it was for pitchers. Below are the ten best and worst hitters by this metric (lower is better).


Whiff Influence Leaders
Name In_Whiff
Eric Sogard -0.0852
Luis Arraez -0.0640
David Fletcher -0.0608
Yandy Diaz -0.0593
Jorge Polanco -0.0584
Mookie Betts -0.0556
Tommy La Stella -0.0531
Robbie Grossman -0.0527
Alex Bregman -0.0518
Ketel Marte -0.0518


Whiff Influence Laggards
Name In_Whiff
Luis Robert 0.1150
Keston Hiura 0.0956
Gregory Polanco 0.0854
Javier Baez 0.0682
Jo Adell 0.0606
Miguel Sano 0.0535
Willson Contreras 0.0525
Avisail Garcia 0.0510
Adalberto Mondesi 0.0501
Franmil Reyes 0.0499


The first thing that you’ll notice is while the leaders and laggards look similar, this is not a straight regurgitation of Swinging Strike rate. The same players appear near the extremes, but the order is slightly different. Adalberto Mondesi is a good example of this. Mondesi is being pitched extremely aggressively by pitchers, owning the third-highest expected whiff rate by my metrics which helps to explain why his whiff rate is so high. That is not to say that is not partially his fault, as he is still 9th worst in whiff influence.


WOBA Influence


Similar to what was discussed above, we can determine the Influence a hitter has over their wOBACon. wOBACON is a function of a number of different skills but is mainly tied to the quality of contact. For hitters, I like to look at this as a given player’s pure hitting skill. These are major league hitters and I am willing to bet that any hitter who gets only fastballs down the middle can hit like Mike Trout over the course of a full season. What makes Trout so special is his ability to hit any pitch and hit it well.

There are a couple of really interesting items that we can glean from looking over the xwOBA and wOBA Influence data. Let’s start with xwOBA.


Hitters Being Attacked
Name xwOBA
Brett Gardner 0.3475
Roman Quinn 0.3473
Josh Reddick 0.3467
Jon Berti 0.3459
Tommy La Stella 0.3450
David Fletcher 0.3449
Andrew McCutchen 0.3449
Nicky Lopez 0.3449
J.P. Crawford 0.3447
Jake Cronenworth 0.3442


Here are the hitters being attacked the most by pitchers. By attacked I mean they have the highest xwOBA on all of their pitches. This list is littered with guys that we would not consider power hitters by any means. These are mostly speed first slap hitter types with a few notable exceptions. The most interesting to me is Jake Cronenworth, the breakout star for the Padres. I am curious if his success is tied to this concept. As he gains more respect, will pitchers begin to change their approach when facing him? On the bright side, he seems to have a positive wOBA Influence. Even as these numbers begin to fall he should remain successful.


Hitters Being Pitched Around
Name xwOBA
Javier Baez 0.3176
Yadier Molina 0.3196
Hunter Renfroe 0.3198
Luis Robert 0.3215
Marcell Ozuna 0.3224
Nick Castellanos 0.3224
Bryce Harper 0.3225
Salvador Perez 0.3229
Hanser Alberto 0.3231
Miguel Cabrera 0.3232


Above are the players with the lowest location-based xwOBA so far in 2020. Now this list is a bit more interesting. One thing that immediately jumps out is the respect that Luis Robert is seeing. Now, this could be a function of his insane swing and miss issues hitting non-fastballs. Regardless, pitchers have taken notice. This makes what Robert has done at the plate thus far even more impressive. Looking at the list you see a few other hitters that are among the game’s best in Harper, Ozuna, and Castellanos. Perez and Baez are both great hitters but pitchers know that they are aggressive and are trying to make them pay for it. Despite his aging-related declines pitchers are still showing Miguel Cabrera a ton of respect and pitching to him carefully.

While it is great to see how pitchers are attacking hitters, the real story comes from looking at the league’s best and worst with respect to Influence. This measure is in my eyes a great way of determining individual hitter skills. Larger numbers here are better.


wOBA influence Leaders
Name In_wOBA
Eloy Jimenez 0.0754
Nelson Cruz 0.0745
Jesse Winker 0.0743
Jose Abreu 0.0723
Fernando Tatis Jr. 0.0716
Luke Voit 0.0708
Teoscar Hernandez 0.0694
Miguel Sano 0.0661
Luis Robert 0.0657
Mitch Moreland 0.0655


Just like we all expected, the best hitter in baseball in 2020 has been Eloy Jimenez. The slugging White Sox outfielder has been great so far slugging 11 homers and hitting just below .300. The model seems to think that what he has done to most improve this season is his location-based expectation. Several other names on this list are among the leagues best hitters thus far and seem to provide some skill-based credence to these mini breakouts.

The massive jumps for Teoscar and Winker seem to be driven by their own contact quality rather than as a function of the pitches they see. It is interesting to see Robert appear again as he has one of the best influences on contact but the worst actual influence on making contact. He is a truly fascinating player and one I hope to watch for awhile.


wOBA influence Laggards
Name In_wOBA
Scott Kingery -0.0522
Eric Sogard -0.0509
Elvis Andrus -0.0489
Jurickson Profar -0.0480
Eduardo Escobar -0.0454
Shogo Akiyama -0.0447
Kolten Wong -0.0433
Adam Frazier -0.0432
Joey Votto -0.0386
Shed Long Jr. -0.0382


Here we have the 2020 laggards. These are the hitters who have performed much worse than the location of the pitches they have seen would indicate. This does not mean that these guys cannot still be effective over the course of a season, they would just need to appear high on the xwOBA list to do so. It is no surprise to see Kingery atop a list like this. A popular breakout pick for 2020, Kingery has been downright awful for the Phillies thus far. There are a few others among the biggest disappointments who find themselves on this list including Shogo Akiyama, who appears to be reacting slowly to Major League pitching. Eduardo Escobar has also been terrible despite a strong 2019 campaign.

The important thing to note with these different leaderboards is that these situations are constantly in flux. These metrics are all reactionary, they will not tell you anything about a hitter with great underlying numbers who is unlucky. This will tell you who improved their expectation the most up until this exact moment. There are some other interesting queries that I can look further into that will help us to better understand hitters.