American expatriate baseball players in Japan have been a feature of the Japanese professional leagues since 1934. American expatriate players began to steadily find spots on Nippon Professional Baseball (NPB) rosters in the 1960s. More than 600 Americans have played NPB, although very few last more than a single season in Japan. Since the 1970s, Americans have also made an impact in Nippon Professional Baseball's managing and coaching ranks, with Bobby Valentine and Trey Hillman managing their respective teams to Japan Series championships.