According to Daily Sports, the Nippon Ham Fighters have more or less decided to part ways with Masataka Nashida after the season (he's in the final year of a 2-year deal). An unnamed source says that finishing in first or winning a Nippon Series most likely won't change that fact.
While the team feels Nashida has done an admirable job as manager of the team since 2008, the club is interested in bringing in someone that can help nurture a young team (someone that's willing to use younger players). They also want to avoid situations where managers and players get too used to each other.
Names that have been dropped as potential candidates: Hideki Kuriyama (baseball analyst, could be the leading candidate), Kazuyuki Shirai (Yokohama Bay Stars Ni-gun manager, was head coach when Trey Hillman managed the team and was also a Ni-gun manager for the Fighters before that) and Tsuyoshi Shinjo (may not be a serious consideration, but the name was apparently dropped by team owner Yoshinori Okoso).