The effect of hitting infield fly balls

An infield fly ball is almost as bad as a strikeout. Think about it: Almost every single ball that’s hit in the air and stays inside the infield is caught. While a rare few do fall for hits, an infield fly balls will probably be caught 95-97 times out of every 100. The only outcome that produces more outs than an infield fly balls? Strikeouts.

The indirect data backs it up. Hitters hit .083 on “soft” fly balls in 2016, according to data from FanGraphs. Even still, only 52.8 percent of those soft fly balls stayed in the infield, suggesting that the batting average of infield fly balls was even lower. Despite the fact that the split itself does not exist, we can assume hitters reach on an infield fly ball around 4 to 5 percent of the time (or even less).

On the flip side, pitchers who generate lots of infield fly balls tend to be more successful. Kyle Hendricks and Clayton Kershaw both are excellent on forcing hitters to hit the weak infield popup while keeping the ball down and out of the outfield.

Kershaw and Hendricks aside, I wonder: Does limiting infield fly balls provide a significant benefit to hitters? And, if so, how much are hitters who limit them helped?

Before I even delved into the research, I came up with two hypotheses:

Hitters with a lower infield fly ball percentage should have a higher BABIP. More balls going into the outfield means a greater likelihood that a defender won’t be able to catch them.

Hitters with a high infield fly ball percentage could also have a high fly ball percentage overall. Hitting fly balls is generally a good characteristic, as long they’re outside of the infield, of course.

So, let’s take a look at both and see what we are able to find.

BABIP

For this one, my theory was fairly simple. Hitters who are able to limit infield fly balls are cutting a BABIP sucker right out of their game. As I already mentioned, most popups go for outs, so players that don’t hit them should have relatively higher BABIPs than those who do.

Since 2010, here’s the graph comparing the percentage of infield fly balls to BABIP of qualified hitters.

As you can see, there’s a correlation between hitters that limit their fly balls and post a high BABIP. An r-squared value of 0.3702 means that 37 percent of the variation in the y-axis can be explained via the x-axis. So, while this correlation is somewhat weak, it definitely exists.

I drew in four arrows showing interesting cases: Joey Votto, Ryan Howard, Rod Barajas and Jonny Gomes. Here’s a quick rundown of each.

Votto

Votto’s infield fly ball rate is extremely low at just 0.7 percent. He has hit just six infield fly balls over the past eight years. Votto also has one of the highest BABIPs, at .357, but that likely does not only have to do with his limiting of popups. Votto is an extremely high contact and line drive hitter, both of which help his BABIP. But it obviously does not hurt that he limits his IFFB rate to practically zero.

Howard

Howard’s infield fly ball rate is twice as high as Votto’s, at 1.4 percent, but is still the third-lowest rate among all qualified hitters. Despite this, though, his BABIP remains at .294. Why is this? Howard, at least during the end of his career, stopped hitting the balls as hard as he once did — since 2010, he has a hard-hit rate of 38.5 percent after putting up a 48.1 percent mark before that. This likely contributes to his lower BABIP.

Barajas

Barajas’ profile is one of my favorites. All he ever did was hit fly balls, and his BABIP fell drastically with it. Almost nine percent of his balls in play from 2010 on were popups. His BABIP took the knife with that, though, as a .235 mark in that time span is about 65 points below the league norm.

Gomes

Gomes hit lots of popups, but still managed to post a fairly decent BABIP, at .304. My explanation? It’s his soft-hit percentage, a career mark he kept at a fairly low 18.6 percent. Being able to square up the balls in most circumstances kept Gomes’ BABIP at an expected level.

IFFB% vs. FB%

My second hypothesis was that players with higher infield fly ball rates may also have higher fly ball rates. And since it’s advantageous for hitters to hit fly balls, popups may just come as an almost “side effect” to those fly balls that they hit.

Using the same data set, we’ll pull up a comparison of players’ infield fly rates versus their overall fly ball rates.

I’m not surprised by the results of this graph. The correlation between a hitter’s infield fly ball rate and their overall fly ball rate is stronger than their infield fly to BABIP rate, and that makes sense. If a hitter hits more infield flies, chances are they will also hit more outfield flies. The data, for the most part, agrees.

Four more interesting cases come up here, so let’s break down Nick Castellanos, Ben Revere, Jose Iglesias, and Rod Barajas.

Castellanos

Despite the fact that Castellanos basically takes infield fly balls out of his game, he still manages to hit fly balls at right around the league average rate. This shows how outstanding of a hitter he is; Castellanos is able to keep his fly ball rate on par with the rest of the league while being able to eliminate the “bad” ones. That’s phenomenal hitting, and it could show just how underrated Castellanos is.

Revere

We all are well aware of the type of player Revere is. He doesn’t hit for any power at all, and he did a decent job of getting on base from 2011 to 2015. It is understandable that Revere does not try to elevate the ball; it would only be a detriment to his game. So, here could be a reverse case, one where the player is knowingly keeping the ball to appeal to one of their strengths. For Revere, that’s just trying to hit singles and subsequently steal bases.

Iglesias

Iglesias has me so confused. He’s an extreme ground ball hitter — almost consistently 10 percentage points above the league average. He also hits a lot of infield fly balls and not a lot of fly balls overall. Despite this, he owns a career .306 BABIP. Iglesias does not have blazing speed, and he does not gather lots of infield hits. So, it’s hard to pinpoint exactly how he keep his head above water, but his career 20 percent line drive rate may have something to do with it.

Barajas

Barajas’ profile is one of my favorites. From 2010 on, he hit a fly ball for more than 60 percent of his balls in play, and he hit an infield fly ball in just shy of 15 percent. He did turn a fair amount of those into home runs, but his aforementioned BABIP suggests that his extreme fly ball tendencies did not work out to create more hits in the long run.

Conclusion

First, I’d like to apologize for my relatively pedestrian use of statistics. Unfortunately, my math education through precalculus has not provided me with the best tools to evaluate data such as this. So, most of this is based off what I have read online about statistics.

Despite that, though, you have to remember that these correlations are not particularly strong. There are outliers on both sides of the spectrum, and I highlighted them a bit above. While infield fly balls may have a somewhat significant impact into a player’s BABIP, hitting more of them does not necessarily mean they will generate fewer hits over the long run.

In fact, this data set is over an eight-year period. I tried to look at similar data from just the 2016 season, and the correlation was significantly weaker — almost six times. I think this says more about BABIP being a luck stat than anything else, but it also suggests that individual players don’t hit enough popups over the course of a single season to see any real impact; this happens more over longer stretches of time.

I think this also shows how good Votto — and potentially Castellanos — are at hitting. Nothing here suggests that infield flies are good, and it seems like there’s nobody in the league that knows that more than Votto, who hit his last popup in 2015. Votto’s so special. He can weed out the parts of his game that are unnecessary for good hitting while keeping what is important. I guess that’s why he has a career .312 batting average.

Most hitters fall somewhere in the middle. They hit popups from time to time, and honestly, that’s okay. There is only one Joey Votto for a reason. But, I do believe that the more they can limit themselves from hitting infield flies while maintaining the ability to hit fly balls overall, the better off they will be.