Identifying Elite Pitchers for ERA - Ground Balls, Walks and Strikeouts Analysis

June 6, 2023

Thunder Dan Palyo attempts to identify the relationship between ground balls, walks, and strikeouts with pitchers' ERA.

Have you set out to prove something and then found out that you were actually, in fact, wrong? What did you do next, admit your error, and move on with your life? Or did you dig deeper because you were still convinced that you might be right and become desperate to find some type of meaning from what you just wasted, I mean "spent" the last x numbers of hours trying to find out?

Well, that's what happened to me here when doing some research on pitchers, something I have become increasingly enamored with over the last several years. I set out to find the data I needed to prove that ground ball pitchers could be more valuable towards your fantasy team's ERA than strikeout pitchers. Strikeouts are sexy and everyone enjoys watching those Pitching Ninja clips on Twitter every day, but I've always had a soft spot for the real grinders who get grounders.

You probably shouldn't be surprised that I have guys like Framber Valdez, Marcus Stroman, and Alex Cobb all on multiple fantasy teams this season. But is keeping the ball on the ground the true key to run prevention as I have believed for many years now or do we now live in the age of the strikeout? And is it possible that strikeouts are the best way to keep your opponent from scoring runs? The quest for answers led me to crunch some numbers and I wanted to share what I found out with you - even I ended up proving myself wrong.

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Ground Ball Grinders

A quick about my methodology for this stat dive - I am using data up through Friday, June 2nd, and I am only considering pitchers who have thrown at least 50 innings pitched so far this season. That ended up being 94 pitchers which gave me a pretty healthy sample size of pitchers who had a solid sample size of innings pitched this year. Again my theory here was that higher ground ball rates would correlate with lower ERAs and that by keeping the ball on the ground, pitchers will naturally give up fewer barrels that turn into extra-base hits and home runs.

Let's talk about the results from my comparison of ground ball rates and ERA first. There are only ten pitchers right now who qualified and are carrying a GB% of 50% or greater so far this year. Here they are.

Definitely some familiar names there - like Stroman who has been among the league leaders for much of his career.  Two Giants are atop the list, both sinker pitchers, and Cobb also has a nasty downward-breaking splitter as well. Bryce Elder is a newcomer to the scene and is a guy who a lot of folks are waiting for regression from and while it will surely come, he still could end up with some really solid numbers.

The ERA sampling here is excellent with just Cabrera (who has been excellent lately after a poor start) and Walker (who has been pretty mediocre) the only guys who are even over 4.0, which is often the unofficial benchmark of what we consider to be ideal for your average starter.

Here are all 94 pitchers from the sample on one of those cool scatterplot graphs. If Jon Anderson thinks he's the only one who can make cool charts at RotoBaller, he's dead wrong! Look at this, I even labeled some of the outliers (if you can't tell I am pretty satisfied with myself).

You can see there's definitely a relationship here, in fact, it's a negative relationship with a correlational coefficient of -.325. In general, we can say that as a pitcher's GB% rate increases that the chance that their ERA decreases improves. This is where Valdez, Cobb, and Webb all serve as examples of ground ball pitchers who are having some huge success in run prevention.

But we can also see that a guy like Cristian Javier can still get it done with only a 25% GB rate and that Taijuan Walker can still be pretty bad even while getting ground balls at a 50% rate. Although we have more pitchers with a GB% of 45% or better below the 4.0 ERA line than above it, getting grounders is certainly no guaranteed formula for run prevention as we have other variables (like walks, more on those here soon) in play.

And if you play DFS, this is also evidence as to why you should probably stack against Jordan Lyles every time out.

Strikeout Kings

So the next to do, naturally, would be to compare strikeout rates to ERA to determine that correlation and then compare it to the ground ball - ERA relationship. Before we do that, here is a snapshot of our strikeout rate leaderboard. I used 28% as the cutoff, so we are left with just 17 pitchers who are striking out 28% or more of the hitters they face this season. Spencer Strider incredibly has an 8% gap between him and the next two pitchers (Ohtani and Greene) in case you were wondering how dominant he's been this year.

We often see high strikeout pitchers also trend towards being fly ball pitchers, so my theory was that we might see some elevated ERAs in this group and that's true of Cabrera, Sale, and Lopez. However, we see a lot of green here as well, including some of the best ERAs in baseball. And we will revisit the assumption that strikeout pitchers and groundball pitchers are mutually exclusive a bit later.

Here's another scatterplot where we can see every pitcher from the 94-pitcher sampling with their ERA and K% charted. We can see Strider head and shoulders above the field with that massive 40% strikeout rate and just under a 3.00 ERA. When you look just below him, you can see a large number of pitchers with strikeout rates between 25-30% clustered up between 2.00 and 4.00 ERAs.

The correlational coefficient for this combo of statistics ended up being -.458, which is another negative relationship and one that is significantly stronger than our GB%-ERA relationship. Like our first chart, there is a negative sloping trend here where pitchers with lower strikeout rates trend towards higher ERAs. Some exceptions would be Alex Cobb (not labeled on the chart but drop straight down from Sonny Gray) who is getting it done with a sub-2.00 ERA and only a 21% K%. And of course, the opposite would be guys who are getting whiffs, but who aren't preventing runs like Chris Sale and then to a much more extreme extent - Lance Lynn (sorry for those with him on their roster so far this season).

So it turns out, not allowing the opposing hitter to actually hit the ball is more beneficial to one's ERA than forcing them to hit on the ground - who knew? I mean, it does make sense. Even groundball pitchers will have a game where they get BABIP'ed to death with a half dozen seeing-eye singles. And your strikeout/flyball pitchers like Sale/Lynn will have games where they rack up Ks but also give up multiple homers as well.

I don't like proving myself wrong, but I like understanding things more than I did when I started. When guys like Jon Anderson say "target strikeouts" in drafts first and foremost - that now makes sense to me as not only do you want to win strikeouts as its own category, but you are also getting ERA while you're at it.

One final thing I wanted to do while pulling all this data was to see how walks affected ERA, too. So let's talk walks!

No Free Passes!

I won't spend too much time on this one as it's pretty intuitive and the data pretty much backs up what most of us probably already knew. Are high walk rates bad for ERA? The conventional wisdom would be that, yes, putting more men on base every game is going to eventually lead to allowing more runs. And with WHIP being a standard category in fantasy baseball, you're already being punished once for high walk rates in that category as well.

The result was a positive relationship of .281 here between walk rates and ERA. Positive just means that when one number goes up, so does the other - it's not a positive thing for your fantasy team, however. It's the weakest of the three correlations, but still somewhat significant. On this chart, we see a slight upward trend from left to right.

I tried to identify some of the outliers in all directions. That group around Nathan Eovaldi is loaded with guys we love who are getting it done with great control. If you go straight up, you'll see the slightly wild, but still highly effective pitchers like Shane McClanahan, Merrill Kelly, and McKenzie Gore (not labeled) who have been able to pitch around those walks.

If you are someone who has Alek Manoah on your roster, I am sure you are already aware of how bad he is this year (and you were warned in the preseason) but even I didn't peg him for this type of regression - yikes. And somehow, poor Thor is the only pitcher with a walk rate under 5% but an ERA over 5.00 - which just shows you how badly he's getting pummeled with batted balls.

Why Not Both?

In a perfect world, we'd want pitchers with both a high GB% and K%. I mean, these two things don't have to be mutually exclusive, right? The reality is that sometimes they are. The type of pitch that leads to more ground balls (sinkers) is often a pitch that batters put in play more often. So if a pitcher is going to throw 60% sinkers (like a Marcus Stroman type), then he's going to cap his strikeout rate to an extent.

But we also have some sinker pitchers who throw incredibly hard these days and a number of pitchers who have successfully paired a downward-breaking fastball with elite secondary pitches. When we look at GB% compared to K%, these guys pop at the top right of the chart.

Again, we see the gap between the field and Spencer Strider, yeah he's good. But the guys I am really looking at here are the Webb, Ohtani, Cabrera, and Brown types. Cabrera is breaking out in a big way right now and if it weren't for his early season walk issues, he would have probably made the cut for my final dream team. Hunter Brown has been incredible and that curveball is the real deal. Logan Webb has long been a guy I love, but he's taken it to new heights this year with more strikeouts while still maintaining an elite ground ball rate.

For the sake of identifying these highly-productive ground-ball-inducing strikeout machines, I used the criteria of a 45% GB% and at least a 24% K%. That gave me a list of just 14 pitchers. But I wanted to incorporate the control aspect here as well since we talked about walks and their effect on ERA as well.

When I set the bar at 8% BB% or lower, we cut that list in half. The list of casualties from the walk criteria is as follows.

Sonny Gray, Merrill Kelly, Shohei Ohtani, Kodai Senga, MacKenzie Gore, Charlie Morton, and Edward Cabrera.

That leaves us with our final list - the guys with the complete package!

Framber leads the way and so it makes sense that he's the featured pitcher on the cover of this photo. He's picked up right where he left off last season and continues to be one of the most consistent pitchers in baseball. Eovaldi is a bit of a surprise, but he's having a career year in Texas and is showing no signs of slowing down. I mentioned Webb already - what a stud! Kershaw gets fewer ground balls than he used to but is having a renaissance of sorts with strikeouts this season so far. The Rays have made Eflin into an uber-efficient pitcher (stay healthy, Zach!) and Hunter Brown looks like a serious ROY candidate after his first two months of starts.

Clarke Schmidt is our outlier here. I am not sure what to say about him other than maybe he has some positive regression coming. His FIP and xFIP are both under 4.0 and his xERA is 4.52. His SIERA is 3.79. He's a guy to keep your eye on this season, he has the trio of things we like, he's just been very inconsistent so far.

Thanks for reading and I hope you learned something - I know that I did!

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