Hoskins, BABIP, and Sustainability

The topic of Rhys Hoksins and sustainability is a big one, because no one believes he will hit 80 home runs a year, but they do want to know how real he is. Today The Athletic Philly wrote about Hoskins and sustainability and this set of paragraphs caught me.

The rest of Hoskins’ success at the plate is no fluke.

The average major league player has a BABIP (batting average on balls in play) of around .300. Through his first 143 plate appearances, Hoskins’ BABIP is .257, suggesting he’s actually getting somewhat unlucky on the balls he doesn’t smash over the fence.The Athletic

BABIP might be one of the most misunderstood stats in baseball. One of the reasons for this is that it was at the center of a large pitching theory (DIPs). DIPs is the basis of FIP and it essentially says that a pitcher has no control over batted balls off of them. The major league average on balls in play is .300 and the assumption was that pitching BABIP trended towards .300 for pitchers over a large enough sample size. This also lead to a belief that batter BABIP actually trended to .300 over time as well. The reason for the trending on pitchers was that the large sample size of batters would average out. It turns out that pitchers have an influence on the type of contact off of them, and that different types of contact are hits at different rates.

Here is what we do know about BABIP:

  • Infield fly balls are almost never hits
  • Home runs don’t count as balls in play
  • Line drives are hits at a high rate (.682), then grounders (.242), and then fly balls where IFFB are included (.130)
    • These categories might still be too broad
  • Minor league BABIP is higher than major league BABIP
  • Other factors like speed contribute to BABIP
  • BABIP is hitter dependent


Now there is an argument to be made that Hoskins has been unlucky on fly balls as he has a .000 BABIP on them. But this is where we get into the HR/FB rate for Hoskins. According to FG’s calculation it is 38.6% this year. If you account for infield fly balls he has actually hit a home run on 17 of 39 outfield fly balls this year. Right now the current leader in HR/FB rate is Giancarlo Stanto at 33.8% followed by Aaron Judge at 32.8%. We are still in small enough sample size territory that this is the difference of 3 home runs of Hoskins’ 17, so he would still be at a historical rate if it were not for some “luck”. This is due to the high number of fly balls Hoskins is hitting. Right now if he qualified he would be hitting fly balls at the 7th highest rate in baseball. What we have seen from other high fly ball rate hitters is a lower BABIP because the ball for the most part either doesn’t count in our calculation or is an out.

The other major predictor of future BABIP is past BABIP. So here is Hoskins the past two seasons as his home run rate has gone up:

AA: .297
AAA: .281

Now part of this is extreme infield fly ball rates at those levels that have not manifest completely in the majors yet (we have not reached a stabilization point for all batted ball data).

The last part of all of this is how we classify luck. We use luck to describe the parts of the system that aren’t explain or that are noise. In theory Hoskins should have a high BABIP based on what he has done so far, but that doesn’t mean what he has done will stabilize or continue. We are still too early to say he will hit line drives at 26.4% pace, and while those are falling for hits at an above average rate now, we don’t know if that is prone for regression. We also know that he is a pull hitter and that various metrics are not going to trend to league average (like ground ball BABIP). One last thing since I mentioned it earlier briefly, stabilization is not the same predictability. We can say that say FB rate has stabilized, but that just means that we can reliably say that measures what he was during that time, it is not the point where we can say that is what he is going forward.


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  1. Steve

    September 14, 2017 06:15 PM

    I agree Hoskins will probably never hit 80 hrs. I do think he will be able to sustain great numbers as a hitter though.
    1) he doesnt expand the stike zone. He seems to have a very good idea of the strikezone and good pitch recognition. He has rarely given away at bats swinging at bad pitches (or watching hittable pitches go by)
    2) when he gets his pitch he hits it…. and hard. It doesn’t even have to be a mistake.
    3) his swing is very controlled and smooth. He’s not the type of power hitter that over-swings trying to hit a home run.

    Now none of this is statistical, more of the “eye test” and the small sample size still applies, but i think it holds relevance. He looks like a very comfortable hitter who has a plan when he steps to the plate.

    This team isnt exactly good yet, but they have quickly become very fun to watch. I cant help but see shades of the 2004-2006 Phillies. Pitching help is needed, Machado would be the icing on the cake.

    • Dante

      September 15, 2017 08:36 AM

      I agree for sure on the pitch recognition. He seems to read the ball immediately out of the pitcher’s hand and is rarely fooled. He has a very balanced swing which helps this too – he doesn’t get caught pulling off or on his front end, so he can react to offspeed if it’s not what he’s expecting. This is a great sign for maintaining a high floor on productivity, and we’ve seen the same through the minors with Crawford, though JP is a bit overly passive in that he doesn’t attack the best pitches to hit like he should.

  2. Mike Fassano

    September 15, 2017 12:15 AM

    It’s all Greek to me. Didn’t understand a single word. Good job though, I think.

    • Romus

      September 15, 2017 09:00 AM


    • Richard

      September 15, 2017 12:53 PM

      You comment a lot at places that rely heavily on such numbers, would it kill you to try to understand some of these things? The stuff Matt is using in this post is fairly easy to understand (there are lots of newer stats that are definitely not so easy). If you did, I think you’d find it’ll enhance both understanding and enjoyment.

      • Mike Fassano

        September 15, 2017 01:00 PM

        Richard. – I love Matt’s writing, but I’m a 67 year old Phillies fan, and mentally I’m dealing with stuff that many others my age deal with. I apologize if I offended Matt or anybody else.

      • schmenkman

        September 25, 2017 10:51 AM

        Mike, I wish you the best in your “real life” situation. My advice would be to ask a question here and there. As Richard says many of the articles today assume understanding of stats, but most writers (and commenters) are happy to answer questions.

        To me the key takeaways from this article are that:
        – first, as background, the Batting Average on Balls in Play (BABIP) calculates how many batted balls are falling in for a hit. The formula for BABIP excludes HRs from both the hits and the at bats.
        – a high number (probably unsustainably so) of Hoskins’ fly balls have become HRs, and so aren’t counted in the BABIP numbers
        – and so while his BABIP might on the surface say that he should be getting more hits (because it’s unusually low), the fact that it’s skewed by the high number of HRs means that’s not necessarily the case

    • pamikeydc

      September 15, 2017 01:23 PM

      Hahaa agree. Very well written, I just didn’t understand

  3. s

    September 15, 2017 02:40 PM

    You hit one of the keys with Hoskins and BABIP to me Matt, and that is that he’s around or below his average. You have to look at things broadly — not like any one stat is going to be “the answer” but the fact that he’s hitting this well without an inflated BABIP, to me, is one good sign among others. Alfaro, on the other hand., has a BABIP 80-100 points over his average which just feels like it’s coming back down at some point.

    Keeping the walk and OBP rate up is another good sign.

    I’d be really interested to see one of those in-depth “hard hit fly ball” and “percentage of hard hit fly balls that went out” studies like someone did for Domonic Brown during his fluke run, where they said there was no way it was going to last. Those numbers were compelling and, even if not *the* reason, they did predict correctly. I suspect we’d find a lot less fluke factor in what Hoskins has done but yes — he’s not hitting 80 HR’s … but wouldn’t that be cool … 🙂

  4. brooklyn boroughboy

    September 15, 2017 05:13 PM

    Rhys Hoskins has hit 18 home runs since he was called up by the Phillies in August. Here are the teams he victimized and the pitchers who threw the go-fer balls with a single stat, HR/9 in parenthesis after their name. Since Hoskins started this hot streak in mid-August there were only 2 series where he did not hit a home run – these were vs. the Braves & Mets.

    Rhys hit 8 HR’s against the Marlins – 3 off of Dan Straily (1.5), 2 off of Vance Worley (1.2) and Brian Ellington (0.7), Dustin McGowan (1.4) and Justin Nicolina (1.5) 1 each.

    Rhys hit 3 home runs off of the Cubs; each of these pitchers gave up 1 HR – Kyle Hendricks (1.2), Jose Quintana (1.2) and Koji Uehara (1.5).

    Rhys has hit 3 home runs against the Padres – Kyle McGrath(1.6), Craig Stammen (1.4) and Travis Wood each gave up 1.

    Rhys hit 2 home runs against the Nationals. The pitchers were Edwin Jackson (2.1) and Oliver Perez (1.2)

    Rhys hit 2 HR’s against the Giants. The pitchers were Ty Blach (1.0) and Kyle Crick (0.6)

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