Over the past decade, a subtle change has taken place within Nippon Professional Baseball, and it has to do with the strike zone, and the way the two leagues’ pitchers attack opposing batters.

Much has been made about the Pacific League’s superior velocity, and while the average velocity has generally been a little higher in the PL, it is certainly true that PL hitters see more four-seam fastballs than those in the CL as well as more splitters, and more balls in the zone.

Starting in 2018, the Pacific League and Central League switched places, with PL pitchers more likely to challenge batters in the zone, and CL hurlers more likely to try and get batters to chase out of the zone.

Why this happened is a matter of speculation, but I will offer a potential explanation for this. It’s a story that starts with the Yomiuri Giants, and a discovery that helped Tomoyuki Sugano dominate the league for a few years.