Why We Care About BABIP

Batting Average on Balls in Play (BABIP) is actually a pretty tried and true part of the baseball vernacular. Sabermetricians may have given it a long name with a fun-sounding acronym, but the principle goes back as far as presidential first pitches and wooden bats. Everyone knows that bloop hits and seeing eye ground balls go for hits quite regularly and that screaming rockets get snatched out of the air by leaping defenders pretty often. You couldn’t find a baseball fan alive who would argue with you on that simple fact.

BABIP is really just the amalgamation of all of those screaming rockets and bouncing grounders. When a batter puts the ball in play, it either goes for a hit or it doesn’t. Sometimes it’s a clean single, sometimes the defender can’t quite reach it. It’s a game of inches and these things happen.

Yet there is another axiom of baseball, one that’s less tried and true, that says these screaming liners that are caught and bloops that find some grass even out. This simply isn’t true, and it especially isn’t true over the course of a few months or even an entire season. Sure, over the course of six years, the number of hard hit balls that get caught and weak grounders that find a hole will balance out, but we don’t judge players in 3,500 plate appearance samples. We judge players based on individual seasons and those lucky moments can really swing the number of hits you rack up or allow.

Let’s walk through a basic example. We’ll even use batting average to make it really simple. Let’s say you come to the plate 600 times, if you have an 8% walk rate, you’ll walk 48 times and if you have a 20% strikeout rate you’ll punch out 120 times. Let’s say you hit 22 HR and don’t get involved in any silly sacrifices, you don’t get hit, or do anything else unusual. That leaves you with 410 balls put into play. The average player will get 123 hits (assuming a .300 BABIP) on those 410 balls in play and will wind up with a .262 batting average.

Now let’s assume that this player got 20 more hits. That wouldn’t even be one extra hit per week and let’s say it’s because the he hit a few bloops that fell in. One extra bloop hit every eight games. That’s a .299 batting average for the season. Less than one hit a week turns you from a .260 hitter to a .300 hitter. The impact of a few extra balls that get through the infield could really make a difference.

And researchers have shown that while certain hitters are capable of running higher BABIPs than others, luck and defense still impact a given hitter’s or pitcher’s results. Miguel Cabrera hits the ball harder than most of the league, so it’s not surprising that more of his balls in play go for hits, but he could easily have 15 or 20 of those balls in play get grabbed or dropped completely due to random chance.

That’s a hard thing for people to accept in the aggregate. We don’t like to accept that randomness plays such a big role in our lives. Cabrera is going to get more hits that most of the league because he’s better than they are, but he’s never going to hit exactly to his true talent level either because weird stuff happens in baseball. Balls take funny hops. Fielders take one step to the left instead of taking one to the right. The ball just happens to find the one lane where no one can reach it even though it was hit at 35 miles per hour.

You’ve seen this happen a million times. It’s baseball. And the evidence indicates that these types of hard luck (or good luck) plays do not even out until you get into multiple years of data for both hitters and pitchers.

A few hits can make a big difference in a player’s stat line, whether they’re a pitcher or a hitter and it’s easy to remember a couple dozen luck-influenced moments for every player each season. Sometimes they even out, but sometimes they don’t.

This is why BABIP matters.

BABIP let’s us see how often a ball falls for a hit when it’s put into play. On average that will happen 30% of the time, but even the best hitters can only shift that to 35% of the time. But the secret is that while hitters will converge on their true talent marks in the long run, the amount the defense and luck play a role in the short run is immense. And even if you don’t want to believe it, a season is a small sample of data in this regard. If you’ve been watching a player run a .320 BABIP for years and this year they’re “breaking out” but have a .370 BABIP, they’re probably just getting lucky.

Let’s consider a couple examples. First, this is the type of play that the Inside Edge system would probably call a remote play, meaning that it gets turned into an out about 1-10% of the time. So when you’re a hitter, this is essentially the kind of swing that should lead to a hit. Whoops.


And now let’s look at this play, which you could easily call routine. It’s the kind of play that should almost never go for a hit. It might look tough but the ball is only about two steps to his left. You can see briefly how upset Dustin Pedroia is.


These aren’t cherry-picked examples, these are just two plays I grabbed almost at random. There have been more than 200 plays this year, according to Inside Edge, in which the batter could reasonably expect to get a hit 90% of the time or more, but a fielder made a play. That probably doesn’t sound like much, but this is just one small slice of the pie. On the other side, there have been something like 1,000 routine plays that have turned into hits.

This is just a simple estimate, but it points to a key concept. Defense and luck play a role in determining if a ball goes for a hit. It’s not just about the batter and the pitcher. We typically want to isolate performance and BABIP can help us do that by showing us who might be the beneficiary of good luck or bad defense.

This is an easy to accept notion at the individual level. Just go watch those two plays again. The next step is to recognize that it can take a while for those types of plays to even out, which means that every players’ numbers aren’t 100% theirs. They’re responsible for a lot of what happens on the field, but some is just outside their control and good analysts try to determine just how much that is.

Think about a ground ball pitcher in front of a bad defense and then think about him in front of an amazing one. He’ll allow fewer hits in front of the good defense and probably fewer runs as a result. Was he a different pitcher? No. Luck works the same way, but it’s even harder for us to observe. We know when a defender is bad, but we don’t know when luck might strike.

As you watch your favorite team over the next week, count how many well hit balls are caught and how many weak ones fall for hits. Think about the number of games that could influence over a full season and then think about why we care about BABIP.

Have BABIP questions? Ask them in the comments!

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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.

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David Speidel
David Speidel

We know that high LD% leads to higher BABIP (in general) and that FB% lowers BABIP. We also know that LD% doesn’t correlate Y2Y very well. What is the range of believable BABIP numbers for someone with league average FB and LD%?

Steve Garcia
Steve Garcia

I see BABIP very differently than the luck aspect you talk about. (Personally I think any ball NOT a strikeout, walk, or HBP as a BABIP. The ball landing in the seats for a HR is no different from a single hit “where they ain’t” – it just gives the better 4 bases instead of 1. Do you discount ground rule doubles, for example? I see NO difference between a ground rule double and a HR, except for the 2 additional bases.)

The basic thing in terms of safe or not is basically hitting it to an open area so that the time it is in the air or grounded into a hole is less than the time the fielders can get to it and make an out with it. It is all TIME based. The shorter time gives higher odds of a hit. Therefore hard-hit balls fall in more often or go through more often. The MLB Stat-Tracker quantifies the velocity off the bat, and in time it will be seen that higher velocities more often go for hits. The “bad luck” you talk about is when it isn’t hit far enough from the nearest fielder. But that really is that a defensive 9 can cover X amount of the field in M milliseconds, and MORE of the field in M+1 milliseconds, and even MORE in M+2 ms, on and on. So, the longer the ball is in the air or a grounder takes to get through the hole the more likelihood of an out.

This nis all conneceted to the seweet spot on the bat. Tom Seaver used to tell that the sweet spot is 1/8″ high and 3″ long – and his job was to NOT allow the hitter to apply that part of the bat to the ball. And he said that if he did that, as the pitcher he’d done his job. The rest of it comes down to did the hitter hit the ball in between fielders? And if so, how short of a time do they have to get to it, before it gets through or lands in the outfield? The shorter the better for the hitter – meaning the harder he hits it, the faster it can get to the safe areas. Every millisecond counts.

Don’t point out when the batter hits it AT someone. That is hitting to the covered part of the field. Yes, it is a statisical thing, but not luck or lack of luck. That area is covered. It is the batter’s job to hit it to the open spaces – and he will a certain percentage of the time. But if he hits it low velocity, the fielders have those extra milliseconds. So, forget the covered areas and only consider the times when it is NOT. Covered areas are 100% outs, essentially.

In the short OF, there is a zone 100% safe zone – in front of the OFers and beyond the IFers. A certain kind of swing and a certain minimum velocity puts the ball there. That is the prime safe zone. Guys with too much loft turn some of that safe zone into an out zone. Guys with not enough velocity also turn some of that zone into an out zone. Hitters who hit the ball hard and force the OFers to back up INCREASE the size of this safe zone. it is another facet of the velocity aspect – (I.e., using that sweet spot Seaver said to not let them do).

Shifts are implemented to shrink the safe zone for a hitter who does not “use the whole field”. BY failing to do that, he re-engineers the field from its objective size to a much smaller “pin-ball machine.” But when the hitter “defeats” the shift by aiming the ball to the vacated area, he totally does NOT have to hit the ball as hard to achieve a safe hit.

Except for that, the whole general principle is to use higher velocity off the bat as often as possible, because that will force the short OF safe zone to be larger – by increasing the spaces between fielders. Which means the ball can be in the air for a few extra milliseconds and still land safely. Notice that it is not often the banjo hitters who get away with bloopers. The defense plays him as if the short OF safe zone is exactly where he will normally hit it and cheat in to shrink that zone.

If the ball is in the air longer than it takes the defense to cover the entire field, there is certainly no luck or bad luck involved. The obverse of that it balls NOT in the air long enough for them to cover the entire field. The harder it is hit the less area they can cover in the time the ball is in the air.

Jaime Garcia this year has a 0.080 Isolated Power stat. He gets 43/8% ground balls, and the batters tend to not hit them very hard. His OBP is .234, his OPS against is a ridiculous .515. Zack Greinke has an even better .506. And both have SLG against of .269. Both have ERAs under 2.00 – the only starters in MLB with sub-2.00. Both of them “saw the bat off” – meaning the hitters are not using the sweet spot. Seaver would spell it out for you that their pitches move outside the 1/8″ x 3″ area – and the pitcher has done his job.

If you watch Garcia, hitters hit WEAK grounders. A weak grounder is a slow grounder – meaning low velocity off the bat because they weren’t able to use the sweet spot. By preventing sweet-spot connecting, the coverage area becomes larger – more time to go in the hole, or more time to catch the fly balls.

It is all about time, and the time is connected to the velocity off the bat. The batter will direct the ball to open areas – safe zones – P percent of the time. That isn’t luck; it is statistics. When he DOES manage to hit it into safe zones – the uncovered part of the field, he must do it normally with authority. It’s not black and white – 1s and 0s – not at all. The uncovered safe zones are safest in the area farthest from all fielders. The farther away fro that center of one of the safe zones, the more likely it will be caught. Especially in those border regions, the ball must be hit harder – with more velocity. And not too high a launch angle. That is where the type of swing comes into play. Or where the pitcher has thrown the batter’s timing off, so that the bat head droops or he is too far out on his front foot. None of these things are luck. The pitcher is out there trying his damnedest to do what Seaver talked about.

MY version of the BABIP – which I developed long before I’d ever heard of the one used by sabemetricians – is based on ALL official ABs that are not Ks – including HRs. Taking HRs out of it actually PENALIZES hitters for really hitting the ball the best. What kind of sense does THAT make? It is contradictory of all common sense.

When I do my BABIP, it is the hard hitters who back up the OFers and IFers who tend to get good numbers. Average for MLB in mine is around .325-.330,varying a bit from year to year. Those who drive the ball tend to have above .330 numbers and weak hitters (low velocity off the bat) tend to get below .325. That is EXACTLY what I want to determine – WHO is giving the fielders sufficient time to catch the ball? It comes down to doubles/HR guys being the best – the guys with higher velocity off the bat. It’s not luck. SOME balls are hit to the covered part of the field – as statistics dictates. And those are outs. So what that it happens? The ball HAS to be hit to the uncovered part to have a chance. Barring errors, which amount to only about 1.5% of the time. It just happens that the covered part of the field for guys like Bogaerts is bigger than for Matt Carpenter or Mike Trout or Nelson Cruz.

Your LD% I assume is line drive %. We are saying the same thing, but it needs to be understood as a TIME thing. Line drives are in the air less long. Line drives come from using the sweet spot, meaning the pitcher didn’t win the battle. It’s a tug of war – pitchers wanting one thing and hitters wanting the opposite. LD% is about hitting the center of the ball with the sweet spot. Exactly so that line drives occur. But it digest down to TIME – fewer milliseconds. The same holds true for hard grounders as line drives. Like I said, the StatTracker should allow quantification of all of this – taking it out of the “qualitative” descriptions – “Line drives”, “bloopers”, “pop’ups”, “fly balls”, soft rounders”, “hard grounders”. It will become “>103 mph” or “<103 mph" or some such value. And launch angles of "12.8°" or "17.4°". "Time through the infield" should become an important metric. And "time in the air".

Steve Garcia
Steve Garcia

It’s all physics

Steve Garcia
Steve Garcia

And physics doesn’t deal with “qualitative”. It deals with “quantitative” – NUMBERS. it is NOT just playing with numbers ala sabermetrics. It is reality turned into data. And then the right approach for dealing with the data. Before StatTracker you had nothing but phrases and terms. Now there are real VALUES that will enable a MUCH better understanding of it all. The physicists might replace the geeky guys in their parents’ basement.

Steve Garcia
Steve Garcia

BTW, Jaime Garcia’s 0.080 Isolated Power number means that only one out of 12 hits is a even a double. Think about what he is doing to the hitters to make them all into banjo hitters. With 7 out of 16 total batters faced hitting ground balls that are being fielded, he is eating them UP. Add in his 24.7% K rate of total batters faced, and he is master of what is going out there. Only 13% – 1 in 8 – is getting any loft to the the OFers. And only 3 out of 16 get hits – a “bunch” of singles and hardly anything more. Nobody is doing JACK against him. If the bugger could just stay healthy!