2020 SABR Analytics: Watch highlights from the Changing Baseball panel

At the 2020 SABR Analytics Conference on Saturday, March 14, 2020, in Phoenix, Arizona, a panel discussion was held on “The Changing Baseball: What We Know, What We Think We Know, and What It Means.”

Panelists included Rob Arthur of Baseball Prospectus; Jay Jaffe of FanGraphs; Meredith Wills of SMT, and moderator Mike Ferrin of the Arizona Diamondbacks.

Here are some highlights:

Changing Baseball panel: Rob Arthur, Jay Jaffe, Meredith Wills, Mike FerrinON THE CHANGE IN COMPOSITION OF NEW BASEBALLS

  • Arthur: “It all started in the second half of 2015. That year, we had one of the largest increases in home run rates from the first half to the second half. … The increase was affecting all the players equally, which is something you would expect if it was a change to the equipment. … Things really accelerated in 2017 and I came up with a way to directly measure the air resistance of the baseball using the Statcast data. … There was a big drop-off in air resistance using that method. Since then, the air resistance has increasingly preceded the home run rate. When the air resistance has gone up, home runs have gone down, like in 2018. When air resistance has gone down, like in 2019, home runs have spiked. It even gets down to a game-by-game level, if you have one batch of baseballs that have higher or lower than average air resistance, you’re going to see more or less home runs per game.”
  • Wills: “The difference between the pre-surge baseballs from 2015 going up to 2018 is that the laces got thicker. The reason that led to an increase in home runs, it sounds counter-intuitive — you’d think thicker laces would relate to higher seams — instead, what seems to have happened is that the laces are made of cotton and wet cotton … is under a lot of tension when it’s stretched and dried. The laces were thinner and not as strong. … In 2019, drumroll please, it turns out the laces have gotten slightly thinner. They’re back to pre-surge levels. And the balls are substantially slicker. It looks like they changed the drying process.”


  • Jaffe: “We’ve seen a big change in batter behavior, with an emphasis on launch angle. … A lot of them have remade their swings. In the grand scheme, it’s a sudden mutability of player abilities. It’s changed our expectations of how a player’s career can proceed. Journeymen are salvaging their careers. … The advantages of hitting the ball in the air are greater than ever before. And that has been a consequence of these more aerodynamic baseballs. It’s created a game that suddenly looks different than the one most of us grew up watching and were familiar with, even five or 10 years ago. … I think we’re at a crossroads here where baseball needs to decide what this game is going to be and how to manage the unintended consequences of what were reasonable changes to the manufacturing of the baseballs.”


  • Wills: “At the moment, the tech does not exist — there is no baseball in the world that is not hand-stitched. There is not a way to do that that is economically viable. … As far as standardization … occasionally I’ll get people asking if I think Rawlings is juicing the balls and my response is no. I’m not sure they are in a position to deliberately juice the ball because even these very subtle differences are creating massive differences in aerodynamics. Until that becomes better understood by the manufacturers, you can’t change it on purpose.”
  • Arthur: “If you look carefully at the drag data from day to day, or even from the regular season to the postseason, it’s much more consistent with random variation. It’s much more consistent with a manufacturing process that’s gone out of control, that they’re not able to effectively determine the air resistance on the baseball. … I don’t think it’s conspiracy theory, but I do think there’s very poor quality control going on. They were warned this was happening as far back as 2017. They should have known about it even before then. Scientists like Alan Nathan have been writing about this for a very long time. … They kind of hide behind a random manufacturing error as an excuse. They could certainly shape the air resistance of baseballs that are going into major-league play if they wanted to. At a minimum, they are sort of negligent about controlling the product that goes onto the field.”

Meredith Wills at Changing Baseball panelON USING A SUPPLY OF ’MIXED’ BALLS IN A GAME

  • Jaffe: “To be honest, that might be sort of the solution, if there was a greater effort to randomize the baseballs and it’s essentially a cross-section of several months of production. … The aerodynamics of a given box of baseballs might have a wider range. … You’re talking about getting a larger sample size and we saw the sensitivity of a small sample size in the 2019 postseason, when we had that early period when there were so few home runs relative to the regular season, and then we saw things returning to normal.”

For more coverage of the 2020 SABR Analytics Conference, visit SABR.org/analytics.


Originally published: March 19, 2020. Last Updated: July 27, 2020.