MLB All-Star - Lesson 03 - Left/Right Splits

Jonathan Bales is the author of Fantasy Baseball for Smart People—a 197-page book created to help you win playing daily fantasy baseball on DraftKings. There are all sorts of stats to use to analyze and predict fantasy baseball performances; from wOBA to ISO to xFIP, you’ll…

By DK Playbook Jun 8, 2020, 9:00pm PDT

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Jonathan Bales is the author of Fantasy Baseball for Smart People—a 197-page book created to help you win playing daily fantasy baseball on DraftKings.

There are all sorts of stats to use to analyze and predict fantasy baseball performances; from wOBA to ISO to xFIP, you’ll never have trouble finding numbers to help you project baseball players. All of those stats, though, should be considered through one filter: lefty/righty splits.

Handedness is such a major part of baseball, but too many daily fantasy baseball players fail to account for how specific batters or pitchers match up with the other in terms of their handedness. And those splits are really, really important.

To give you an idea of how important, I charted OPS for the top 150 hitters since 2000, broken down by matchup. You can see that left-handed batters struggle the most versus southpaws, while righties are worse against right-handed pitching.

It’s interesting to see that there’s a slightly larger gap for lefties based on the handedness of the pitcher. I researched the number of at-bats per home run for these same 150 players, and those results are even more extreme.

The top left-handed batters since 2000 have taken right-handed pitchers deep once every 22.2 at-bats, compared to once every 32.2 at-bats against lefties—a 45 percent difference, which is huge. Right-handed batters have also been better against the opposite handedness, but the results aren’t nearly as extreme. That means that lefties rely more on the pitcher’s handedness for production than righties, especially for power numbers.

For more evidence of this effect of handedness on hitting, check out these 2014 ISO heat maps, courtesy of FanGraphs. The first is how righties hit off of right-handed pitching.

The highest ISO/P numbers unsurprisingly occurred over the middle and inner portions of the plate, and they’re as high as 0.089. Meanwhile, here’s the lefty vs. lefty heat map.

The highest total is just 0.078. Simply put, lefties struggle against lefty pitchers way, way more than righties versus right-handed arms.

If you’re analyzing an individual player in a single matchup, his career splits are going to be more valuable than overall numbers. Some lefty bats don’t struggle as much versus lefty arms as others. I think it makes sense to consider aggregate numbers when you don’t have a sufficient sample size of data (such as with a rookie or second-year player), but generally individual splits trump overall splits (though the two often resemble one another).

In tournaments, though, a popular daily fantasy baseball strategy is to stack players on the same team—the 2-3-4-5 hitters on a single offense, for example—in which case I think it makes sense to consider the overall rates. You’re not going to find an entire offense of left-handed hitters who collectively hit well against left-handed pitchers, for example.

If there’s one actionable item to take from this data, I think it’s that you can run primarily right-handed stacks out there against both lefty and righty pitchers, but you need to be more careful with lefty hitters, who can be in a really poor spot against not only lefty starters, but also lefty relief.

Of course, the flip side of that argument is that lefties are much better against right-handed pitching. If DraftKings players are typically priced according to their overall numbers (which is probably the case), then lefty bats against right-handed pitching will offer more value than righties versus lefty arms (because of the larger deviation in splits for lefty batters).

That means that rolling out a primarily left-handed stack against a right-handed pitcher might offer both value and upside, which is ideal in any tournament. Of course, it’s still a risk given that a left-handed stack will often face left-handed relief, which could result in 1) poor matchups for your hitters late in the game or 2) even worse, your hitters getting pinch-hit for with a righty bat.

Looking at this data and thinking about how managers work in the final few innings of baseball games, I think it’s safe to say that right-handed batters are far less volatile than lefties since their power isn’t so reliant on a specific handedness of pitcher. And since much of winning a tournament is about maximizing the overall probability of your bats realizing their upside, you could make an argument that righty-dominant stacks as a whole trump left-handed stacks.

How to Research and Implement Splits

You can find a hitter’s splits pretty much anywhere—from FanGraphs to ESPN. I still analyze the stats that I consider to be most vital, such as wOBA, but I never consider overall numbers—just those against the handedness of pitcher that a batter will be facing in a given game. I specifically target hitters who are extreme in their splits, because they’re more likely to be mispriced based on their overall numbers.

One thing to keep in mind is that your analysis for a batter is very straightforward—him versus the starting pitcher (we’ll ignore relief for now)—whereas pitchers face an entire lineup of hitters. That means that lefty/righty splits are generally more important for hitters than for pitchers. Some lineups can be dominated by right-handed hitting, however, in which case a pitcher’s lefty/righty splits can matter a lot more. The Astros are a primarily right-handed team that has the potential to crush left-handed pitching, for example.

Finally, it’s important to keep in mind that you always need to analyze things from both ends. Some daily fantasy players look at a hitter’s lefty/righty splits and then either play him or avoid him based on how he performs without ever analyzing the pitcher. When a right-handed batter who crushes right-handed pitching matches up with a right-handed pitcher who excels against righties, the effects might cancel one another out. If you fail to analyze the pitcher, you might anticipate the batter being in a more favorable spot than what’s actually the case.

Also, although most lefties are best against righties and most righties best against lefties, that’s not a universal thing. Some guys are “reverse splits” players who actually perform best against the same handedness of pitcher.

I typically start my splits research with pitchers to see which ones struggle against a particular handedness of hitter. That allows me to look at entire offenses to see which hitters might match up well. I analyze the splits for the entire order to see which batters also match up well with that particular handedness of pitcher. Ideally, you’d always like to be playing hitters who excel against a particular handedness of pitcher and are facing a specific pitcher who struggles versus that hitter’s handedness.