Arthur: The baseball isn’t rejuiced; it’s just inconsistent

From SABR member Rob Arthur at Baseball Prospectus on October 25, 2019:

After the discovery of increased drag to start the postseason, people started to see every fly ball as evidence of the Commissioner controlling the home run rate. The ones that fell in the dirt or outfielders’ gloves were taken as positive proof that MLB had dejuiced the baseball. The ones that made it over were debated over by people launching ever more elaborate searches on Baseball Savant to determine just how likely or unlikely a given batted ball is to become a home run, given its exit velocity and launch angle. A factor that many baseball fans had never thought about — fluctuating air resistance — was suddenly at the top of everyone’s mind, pulling each deep fly back from the stands.

Now that the home run has returned — eight dingers have been hit in only two World Series games — some people are clamoring to know whether MLB did something to the baseball again. But the truth is more complicated than the story about the initial surge in air resistance. Instead of a clean increase or decrease in drag, it seems like every game is a different animal with a new kind of baseball. Each contest has a new level of air resistance that is responsible for several feet more or less carry on fly balls. The trend at the beginning of October has given way to aerodynamic chaos.

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Originally published: October 25, 2019. Last Updated: October 25, 2019.