Advanced MLB DFS Strategy: Sneaky Stacks Against Reverse-Splits Pitchers

With Opening Day of the MLB season right around the corner, it's time to start getting your mind right and preparing for a full season of MLB DFS action. Last summer we missed out on several months of MLB games due to the COVID pandemic, but we are going to get 6 months worth of DFS and for those of you who love to grind, I will be here all Spring, Summer, and Fall grinding with you and anchoring our MLB DFS premium coverage here at RotoBaller.

In this series of articles, I am going to try to lay out a number of overlooked factors that can be exploited by savvy MLB DFS players. Baseball is such a stat-nerd sport, and there are so many different statistics that one can consider when trying to break down any slate of games. I'll cover the basics for both hitters and pitchers in my annual DFS Strategy guide, but for today I want to focus on an often under-analyzed angle - and that's targeting reverse-splits pitchers.

Far too often do we just assume we want to stack hitters with the platoon advantage against a pitcher or we leave a hitter out of our stacks that we shouldn't because they're facing a pitcher with the same handedness. But there are a lot of right-handed pitchers who actually better against lefties and vice-versa. And some pitchers are equally bad to hitters from both sides of the plate. If you really want to get a leg up on the competition, you should be looking to gain leverage on the field by stacking righties and against righties and lefties against lefties when the situation calls for it. I did some research recently on FanGraphs to try to find which pitchers were the most exploitable against hitters from the same side of the plate, let's take a look.

RHP vs. RHH: 2020 xFIP

One thing to note is we have a lot more data to work with here with righties vs. righties because there are simply more right-handed hitters and more right-handed pitchers. Here we have all starting pitchers from 2020 with at least 20 innings of at-bats against right-handed hitters who had an xFIP of 5.00 or higher. When we compare their xFIP against righties to their xFIP against lefties, we can see which pitchers reverse splits and how drastic they were.

Roark and Stripling tied for first here and were significantly worse against righties. They are followed by Trevor Williams and Anibal Sanchez. Erick Fedde was only mildly worse against righties while the rest of the field was actually worse to lefties (meaning they were pretty bad to hitters from both sides of the plate). Mike Fiers is a guy I wasn't surprised to see here as he's been a reverse splits guy for most of his career and Dylan Cease was a bit of a surprise, too, since he flashed some upside at various points in his career so far.

RHP vs. RHH: 2020 wOBA

I wanted to look at another metric that is popular in MLB DFS, and that's wOBA (weighted on-base average). Again, I filtered out relievers and went with all righties who allowed a .400 wOBA to right-handed hitters last season with 60 total batters being the minimum. What we see here is everyone except Touiki Toussaint having reverse splits in wOBA allowed. The bigger differences belonged to Michael Fulmer, Tanner Roark, and Anibal Sanchez. Roark and Sanchez made our first chart, too. Guys like Nathan Eovaldi and Adam Plutko were actually pretty good against lefties, but bad against righties, while guys like Zack Godley and Asher Wojciechowski were just pretty bad to hitters from both sides. Michael Wacha is a guy I've stacked righties against now for a few years and also fits the description of "decent vs. lefties and bad vs. righties."

A lot of our righties with reverse splits are changeup pitchers or guys who throw a lot of breaking balls. Some guys who didn't make the list here but have historically had fairly wide reverse splits are Kevin Gausman, Jake Odorizzi, Chase Anderson (the cover boy), and Lance McCullers Jr.

LHP vs. LHH: 2020 xFIP

When we look at lefties, we are going to be dealing with a much smaller group and there are some pretty decent pitchers on this list. For this group, we have lefties with an xFIP of 4.3 or higher against LHH with a minimum sample size of 40 total batters faced. We have some smaller samples than usual from 2020 since it was a much shorter season so we have to take everything with a grain of salt to an extent.

Our most drastic split here belongs to Max Fried, who is a pretty good pitcher, but just wasn't good against left-handed hitters last year. Fried is followed by Martin Perez, who had a solid season in 2019 but regressed back to his mediocre ways in 2020 and was pretty bad against righties, too. Marco Gonzales had the third-highest split and is a guy who's showed some slight reverse splits throughout his career.

Going into this stat dive I thought for sure that Tyler Anderson would have shown reverse splits as he's a guy I've picked on with left-handed hitters for several seasons now. But it turns out he was just terrible to hitters from both sides and was especially bad against righties. Like with the righties, we see a pattern here with the type of pitchers that we are seeing with a lot of these guys being cutter, curveball, and/or changeup pitchers. Perez and Minor are two guys who revitalized their careers by becoming cutter/change-up pitchers but it's made them more hittable to lefties.

LHP vs. LHH: 2020 wOBA

When we look at wOBA (.300 wOBA or greater allowed to lefties, minimum 40 total batters faced) the results are a lot less pronounced than they were with right-handers. The only two really big splits here belong to Anderson and Gonzales, and it should be noted that Gonzales was really good against righties with the best results of anyone on this list by a wide margin. Patrick Corbin and Madison Bumgarner were traditional split guys who had down years altogether so I wouldn't read too much into those results, especially with Corbin being a fastball-slider guy.

Andrew Heaney and Yusei Kikuchi had almost perfectly neutral splits and probably could have been excluded from the list as a .300 wOBA isn't all that bad. I simply had to lower the threshold to .300 just to get enough left-handed pitchers with enough of a sample size to draw some comparisons.

Summary

1. I love studying pitchers and pitching stats. Look for a brand new daily column called the "RotoBaller Pitching Primer" that will be a featured piece of our RotoBaller premium DFS package this season. I'll be anchoring that piece with several of the other RotoBaller MLB DFS writers and it's going to take things to the next level.
2. Now that my shameless plug is out of the way, I think it's really important to know as much as we can about starting pitchers before we stack hitters against them. We shouldn't blindly stack all righties or lefties against pitchers without knowing their splits.
3. Some guys who are solid overall pitchers, but struggle with hitters of the same-handedness are good guys to target with one-offs or small stacks.
4. Some pitchers are just really bad or totally mediocre and should be targeted with hitters from both sides of the plate.
5. Using hitters against the same handedness of pitcher is going to make your lineup more unique, and we should definitely do it more often - as long we study the spot closely and make sure it's the right move!

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