Ask any baseball fans about their most thrilling moments, and the chances are high that a moment related to a home run will get the most votes. They are widely considered the most exciting and attractive plays in baseball. However, the recent report suggests that Japan’s NPB might have taken home runs a bit more seriously than required. 

While high-impact plays provide immediate offense, dramatic, long-distance action, and are frequently viewed as the ultimate goal in baseball, NPB’s reported manipulation to leverage the same revealed an uneasy secret.

“According to confidential information obtained from a certain team, at an executive committee meeting of the 12 professional baseball teams held on August 4th last year, it was decided that because the trend of pitchers dominating at the plate has continued for several years, we will aim for the highest value within the standard range of the coefficient of restitution, and we will instruct Mizuno, the manufacturer of the unified ball, to do so,” Yahoo Japan reports.

Be it MLB or NPB or in the larger baseball scene, pitchers have traditionally dominated baseball through high velocity, movement, and advanced, technology-driven training, making hitting increasingly difficult. For reference, it is extremely difficult to make contact against pitchers like Paul Skenes and Tarik Skubal in MLB. Their deceptive techniques make hitting a tough nut.

Same in NPB, Shunpeita Yamashita’s 100 mph fastballs are considered one of the toughest for the hitters. However, the report suggests that NPB secretly planned to reverse the traditional dominance of the pitchers and make the game more batter-friendly. How? By making the official ball harder and achieve the highest possible “coefficient of restitution.”

NPB uses a “unified” ball by Mizuno. All 12 teams use this leather-covered ball, which is known for having a slightly smaller, tackier, and more textured feel compared to MLB’s Rawlings balls, aiding in grip. Now, last year, Mizuno was reportedly asked to make “the ball harder by tightly winding the yarn.” The harder the ball, more coefficient of restitution it will generate.

But the worst part was that, apart from manipulating the ball, NPB was also caught lying about it.

Reportedly, back in 2013, the coefficient of restitution was set at 0.4134. But with a harder ball now, the range increased to 0.4154 and 0.4194. With a higher coefficient of restitution, the ball bounces more, and thus, the chance of home runs increases. Still, despite going over the set value, it was reported as “high value within the rules.”

Currently, there are 132 games played in the 2026 NPB season and 184 homers already scored. This puts around 1196 homers by the end of the season, which will cross the 1096 home runs scored last year. Fans might be loving it, but the manipulation of the ball is putting NPB’s authenticity in question.

MLB faced the same controversy as NPB

What NPB is facing currently, MLB faced it back in 2019. A record-breaking 6,776 total home runs were hit in the MLB during the 2019 regular season. This total surpassed the previous record of 6,105 set in 2017 by 671 homers, marking the highest volume of home runs in league history at the time.

Questions were raised, and MLB was forced to investigate by a committee of outside experts. They focused on the performance of baseballs and the increased home run rates during the 2017 and 2019 seasons. However, reports went in for MLB. It was concluded that there was an obvious change in the balls that caused more home runs. But the changes were unintentional. Rather, due to the inconsistent baseball seam heights, the seams were producing far less drag.

So, although the balls were looking juiced up, it was just manufacturing variability.

“No evidence was found that changes in baseball performance were due to anything intentional on the part of Rawlings or MLB and were likely due to manufacturing variability,” the committee concluded.

Since then, MLB’s recent efforts have focused on balancing gameplay between the pitchers and batters. However, NPB might have targeted a home run grandeur, making the league more thrilling and engaging.