MLB finally admits changes to ball itself fueled home run spike, but doesn’t say how or why

By Dave Sheinin
May 24 at 5:30 PM

Major League Baseball on Thursday confirmed for the first time something pitchers in the sport have been saying for more than two years: that changes to the composition and/or behavior of the baseball are responsible, at least in part, for the surge in home runs since the middle of the 2015 season. What remains unexplained, however, is what exactly those changes were, or why they occurred.

A committee of 10 scientists and data specialists, formed by Commissioner Rob Manfred, concluded in a report released Thursday that home run surge can be explained, at least partially, by “a change in the aerodynamic properties” of the ball — specifically, “reduced drag for given launch conditions.”

The home run surge “is not due to either a livelier, ‘juiced’ ball, or any change in batter or pitcher behavior,” the report concluded. “It seems, instead, to have arisen from a decrease in the ball’s drag properties, which cause it to carry further than previously, given the same set of initial conditions — exit velocity, launch and spray angle, and spin. So there is indirect evidence that the ball has changed, but we don’t yet know how.”

“The great mystery is: What in the world has happened that we’ve had a small change in drag — it isn’t large — but one that seems to be systematic enough that it’s affecting offense,” said committee member Lloyd Smith, a professor of mechanical and materials engineering at Washington State University. “We’ve done every test you could imagine, and we just couldn’t nail it down. It’s in there. It’s in the data someplace. But it’s going to take a lot more time and effort [to solve].

-snip-