Which is Better? A Ground Ball Pitcher or a Fly Ball Pitcher
It’s very likely that if you’ve spent any time at all reading sabermetric analysis that you’ve heard some mention of a pitcher’s batted ball profile. You might have seen a reference to a guy being a “ground ball machine” or an “extreme fly ball pitcher” and perhaps you wondered to yourself, “which is better?” Would a pitcher be better off as one or the other?
In reality, there’s no ideal batted ball distribution for a pitcher, just like there’s no perfect distribution for a hitter. Pitchers would love to never allow line drives and get tons of infield fly balls, but within the realm of possible outcomes, you can be successful as a ground ball pitcher or as a fly ball pitcher. One isn’t better than other, they’re just different.
Let’s take a look at a little bit of data to get started. Here are the results on each type of ball in play from 2014:
You can see that line drives are bad news for pitchers any way you slice them. They lead to more hits and huge run values compared to the other types of balls in play. But there’s a trade off in the ground ball-fly ball department. Ground balls go for hits more often than fly balls but fly balls go for extra bases much more often when they do drop in for hits.
In other words, if you’re a fly ball pitcher, you can usually sustain a below average BABIP, but you might get tagged for a few extra doubles, triples, and homers as a result. Ground ball artists, on the other hand, don’t often allow homers and extra base hits, but they allow singles to squeak through more often.
If you’re perfectly average, you’d likely prefer to induce a ground ball to a fly ball, but it depends on the situation, your park, your defense, and your particular arsenal. It’s not a simple relationship, as the better you are at getting ground balls the less likely they are to hurt you and the more likely you are to get fly balls, the less likely they are to hurt you. Head over to our entry on batted ball stats and SIERA to learn more about that relationship.
Now let’s consider this from a different angle. Let’s divide pitchers up into four equal groups based on their ground ball rate and look at their ERA- and FIP-. Below is a table that does just that using pitcher seasons from 2014 of at least 100 innings (n = 149):
|Above Average GB%||92||91|
|Below Average GB%||97||100|
We know that ground balls generally have a lower run value than fly balls despite their higher BABIP, and in general, pitchers who throw more ground balls perform better overall. But it’s not simply a matter of more ground balls always helping. There’s a point at which more ground balls doesn’t really change things and it’s not like this is an extremely strong relationship.
There’s another interesting wrinkle to consider. Balls that are pulled, hit up the middle, or hit the other way are also different in terms of their potential damage. Max Weinstein found, for example, the ground balls the other way are worse for the pitcher than ground balls that are pulled, but line drives and fly balls are much more dangerous to the pull field.
Ideally, you want to get batters to pull the ball on the ground and hit it in the air the other way. Pitchers can only control the type of batted ball and spray to a degree, but pitchers who find themselves hitting these marks will allow fewer runs.
There’s also an issue of HR/FB%, which is measured exactly how it sounds, and indicates how often a pitcher allows a home run for every fly ball. This is important because this number takes a while to “stabilize.” If you get unlucky on a ground ball, you’re allowing a single and the occasional double. If you get unlucky on a fly ball, it might clear the fence. This is why we have statistics like xFIP, which try to approximate a player’s performance had they allowed a league average HR/FB%.
But that xFIP value is based on the pitcher’s fly ball rate, because we expect pitchers who allow more fly balls to allow more home runs. But again, if you’re an extreme fly ball pitcher, that effect can turn around.
Essentially, there’s no magic batted ball profile. Ground ball pitchers typically do a little better on average but there are plenty of terrific fly ball pitchers as well. You can make more mistakes on balls in play if you have a high strikeout rate or a low walk rate, too, but those are related to the quality of contact you allow. And quality of contact is really what it comes down to. A ground ball isn’t a uniform thing. There are all sorts of ground balls hit at different angles and velocities.
A 47% ground ball rate sounds perfectly fine, but it doesn’t tell you the whole story. You always need to include more data in your analysis, but batted ball numbers can tell you something about the potential strengths and weaknesses of a given pitcher. If you have a fly ball guy, you know it’s pretty likely he won’t allow that many singles (relatively speaking), but that he might get tagged for a few dingers every now and then. If you have a ground ball pitcher, you’re not going to see the extra base power but you might watch a few rallies get going on four straight singles.
We’re talking about a trade-off, not an ideal type. It’s about the way in which a pitcher gets their outs and what you really care about is that he’s getting outs, period. If you see a pitcher with a certain profile, however, and the outcomes aren’t lining up, that’s when you might get curious. If you run into a ground ball pitcher with a .250 BABIP, take caution and prepare for some regression in all likelihood.
One type isn’t better than the other, they’re just different. You can be good, bad, and in between no matter your rates.
Neil Weinberg is the Site Educator at FanGraphs and can be found writing enthusiastically about the Detroit Tigers at New English D. Follow and interact with him on Twitter @NeilWeinberg44.
Bill James always wrote that he perfered fly ball pitchers over ground ball pitchers. I think his reasoning behind it is that he didn’t think ground ball pitchers got a lot of striekouts , and he thinks to be a great pitcher you need a a good to great strike out rate.
What are your thoughts on this?
You can probably make this case in general as the kinds of pitchers that get strikeouts also generate fly balls, but there are also plenty of fly ball guys who don’t get a lot of strikeouts. Might be harder to be great as a ground ball guy, but I don’t think it’s harder to be good.
Great article! How were the splits (Lowest to Highest GB% rate) defined?