NPB-to-MLB Translation

In this study, I explored the performance trends of current MLB players who previously played in Japan’s Nippon Professional Baseball (NPB) league. To gauge how these players transitioned, I calculated the average career statistics of former NPB players in two stages. First, I averaged their NPB career stats, providing a baseline of their performance in Japan. Next, I calculated the averages of their MLB career stats, capturing their performance in the U.S. By comparing these two averages, I derived the typical statistical differences between NPB and MLB performance levels. This analysis sheds light on how player metrics generally translate across these leagues, offering insight into the challenges and adjustments associated with the transition from NPB to MLB.

The results were not particularly surprising, as it’s expected that player statistics would generally decline when moving from NPB to MLB, given the differences in competition level. However, the study reveals just how much these numbers typically decrease on average, providing valuable insight into the degree of adjustment players face. This analysis offers a strong predictive model for assessing potential MLB performance for players transitioning from NPB, giving teams a useful tool for evaluating and forecasting talent.

Despite the typical decline in performance when players transition from NPB to MLB, both pitchers and hitters generally still perform at an above-average level in MLB.

One statistic I found particularly interesting was that, on average, pitchers' K% actually tends to increase, specifically by 1.47%. While plate-discipline metrics in MLB and NPB are very similar, baseball in Japan is generally considered more "contact"-oriented, leading to fewer strikeouts. This shift in K% provides an intriguing insight into how pitchers’ effectiveness can translate across leagues.