MLB finds seam heights, new batting techniques led to HR surge

A study commissioned by Major League Baseball attributed the 2019 season's surge in home runs to inconsistent seam heights on balls, as well as "changes in player behavior" that led to altered launch angles and exit velocities, according to ESPN's Jeff Passan.

"Analysis of StatCast data shows that the increase in home run rate between 2018 and 2019 was due in part to a change in launch conditions and in part to a change in the baseball drag," the abstract of the study's preliminary report reads, according to Gabe Laques of USA Today. "The laboratory experiments, using newly developed techniques, show a correlation between drag and seam height, with the average seam height in 2019 smaller than in 2018 by less than 0.001 inches."

It states: "No evidence was found that changes in baseball performance were due to anything intentional on the part of (baseball manufacturer) Rawlings or MLB and were likely due to manufacturing variability."

The report also suggests a deeper look into a batted ball's spin is needed. Those involved offered some ways to improve the tracking of baseballs but noted this is merely a preliminary summary and they are working on a "more detailed report," according to Passan.

A record 6,776 regular-season homers were hit this past season. Both the Minnesota Twins and New York Yankees surpassed the 300 mark, with the former's 307 home runs setting a new single-season record. The Baltimore Orioles, meanwhile, became the first team ever to allow 300 long balls in a season, finishing at 305.

The power surge trickled down to the minors, too, as both the International League and Pacific Coast League switched to MLB's baseballs instead of using their own. As a result, both Triple-A circuits reported home run rate increases of nearly 60%, Jayson Stark of The Athletic reported in August.

Many of the game's biggest stars, including Houston Astros ace Justin Verlander, called for MLB to take ownership of what players feel are doctored baseballs. Verlander blasted the league and Rawlings for their inaction on the issue; commissioner Rob Manfred later denied that the league juiced the balls.

Rawlings president and CEO Michael Zlaket also denied such modifications during a press conference Wednesday in San Diego.

"We have never been asked to juice or de-juice the baseball, and would never do something like that on our own," Zlaket said, according to Kyle Glaser of Baseball America.

Players and coaches then said the baseballs were altered again for the postseason to decrease the distance that balls traveled.

A previous study released in May 2018 found that the home run surge between 2015 and early 2018 was due to "a change in the (baseball's) aerodynamic properties" that resulted in "reduced drag for given launch conditions," according to Dave Sheinin of The Washington Post.