Analyzing Pitcher Fly Ball Data for Fantasy Baseball 2023

Pitchers don't have much of a say about what happens after a pitch they throw is put into play. There is a ton of randomness that occurs after a hitter makes contact with a ball, and that makes a lot of pitching statistics hard to trust.

Getting ahead of this gives us an advantage. We can have a pretty good feeling about which pitchers were lucky and unlucky, and therefore what direction their future statistics are more likely to go in.

Today, I want to zoom in on fly-balls allowed. We will go over the category, look at some numbers and correlations, and then dig up some applicable takeaways for the 2023 fantasy season.

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League Data

Here is a breakdown of what happened when a fly ball was hit in 2022.

So you are mainly looking at a flyout or a home run. The event with the biggest impact on the stats is the home run. Here's how that rate has changed over the last five years:

We see the spike in 2019 with the juiced ball, and then a 2020 season that was so short it should just be ignored - and then a decline in this category over the last two seasons.

Note that I am using Baseball Savant's classification model for this, not FanGraphs. You will get a number closer to 10% if you use FanGraphs because they count infield fly balls as fly balls while Savant does not.

What Do Pitchers Control?

The next question to ask is do the rules apply to everyone evenly? Should we expect a 15% HR/FB for every pitcher, or are some pitchers better or worse than others at this? Let's just take a look at the top 10 highest HR/FB rates from 2021 and see how they followed up in 2022:

Of the top 10, only Gray and Kikuchi got worse, and most of them saw significantly lower numbers the following year. If we cluster them together, we find that pitchers that went above 20% in 2021 average 16% in 2022. The pitchers who were under 10% in 2021 averaged 17% in 2022. The correlation coefficient here is 0.17 - which means the two lists are not related.

This means that a pitcher has very little to nothing to say about what HR/FB they allow - and it's best to just assume 15% for everybody in the future.

Park Data

The one thing that does stay constant year-to-year is park factors (unless they change the dimensions of parks in the offseason, which is becoming more and more common). The worst place to allow a fly ball over the last two seasons has been Great American Ballpark in Cincinnati. 20% of the fly balls there have gone for homers. At the bottom of the list is Comerica Park in Detroit where only 11.2% of fly balls have gone for a homer (note: Comerica is changing their dimensions in a hitter-friendly way this offseason).

Here is the full data on that:

You can see steady domination by Cincinnati. You can also see what a big difference park changes can make, as Camden Yards went from 22% (second-highest) to 12.5% (sixth-lowest) with that left field wall change.

This should lead us to project a rate above 15% for Hunter Greene and a much lower than 15% for Brady Singer - just to take a quick example there.

Pitcher Standouts

Since we know that we should be regressing the extremes toward the mean, now we can look for these extremes and upgrade or downgrade them accordingly. It's important to note that the rate of allowing fly balls is something a pitcher controls. K% is very steady year-to-year (correlation around 0.7) and so is FB% allowed (correlation around 0.65). If you're striking out 30% of the hitters you face and earning a 50% ground-ball rate, there is very little difference that can be made by the HR/FB because you're just not allowing many balls in play. We will take this into account moving forward.

What I did now is basically replay the 2022 season using a regressed HR/FB for each pitcher. I did include park factors here, so we are still penalizing or rewarded pitchers for where they pitched.

The long and short of it is I found how many fly balls each player allowed and then came up with an expected home run total based on that 15% HR/FB, adjusted for the home ballpark (I only took half the overall effect since pitchers pitch about half their games at home). First, I'll show you the biggest differentials in the negative frame - these are pitchers that allowed fewer homers than they were expected to.

Holy cow on Martin Perez! Giving up 11 extra homers would mean something like 15-20 extra earned runs. If we add 15 earned runs onto his total, it takes his ERA from 2.89 to 3.57.

At this point, I realize that I'm basically just talking about xFIP. Perez's xFIP was 3.80 - so yeah, it checks out.

Fried and Manoah are also super notable here as pitchers who had elite ERA marks with lower strikeout rates. Fried has been doing this long enough that maybe we just have to admit that he's solved the puzzle of soft contact, but that hasn't really been true in HR/FB for him as he allowed a 16% mark in 2021, a 27% mark in 2019, and a 27% mark in 2018 - so he's been all over the place there.

Manoah put up a 15% HR/FB in 2021 and then brought that down in 2022 to what you see above. More potential bad news for him is that the Rogers Centre is changing a bit this offseason, and if it makes any difference, it will likely be in the hitters' favor. Manoah is young and skilled enough to cancel out this regression with a higher strikeout rate - and maybe we should just expect that to happen, but it's a bit alarming to see him pop up this high on the list.

Now, let us look at the other end of the spectrum - the bad-luck pitchers:

The top two players here also gave up a ton of homers on fly balls last season, and we saw them both in the first table we cited here. Maybe that means that something these guys are doing is making their pitches much easier to square up, that's certainly possible. Figuring that out right now doesn't seem very important in these two cases since neither of these guys is being drafted in most leagues right now - although Gray does still pique some interest with his former prospect pedigree and the good whiff rates he's posted in his young career.

Ray, Morton, Cole, and Musgrove are the only obviously fantasy-relevant pitchers on this list, and it's likely they all benefit from regression in 2023.

Do you want the full data? Of course, you do! Here it is, all 429 pitchers that allowed at least 25 fly-balls last year along with the rest of the numbers we've cited above. The "FBHR" column is how many homers they allowed on fly balls. It might not exactly match their HR-allowed totals since you can allow a home run on a line drive as well. Check it out, enjoy it, and send me your thoughts and takeaways - and I'll talk to you later on!

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