Hiroshima Carp manager Marty Brown is not returning to the club next season after Sunday's loss to the Yokohama BayStars eliminated them from contention for the third and final playoff spot.
The Carp needed to reach the postseason for his contract to be extended. Former Carp infielder Kenjiro Nomura is expected to succeed the 46-year-old American.
Hiroshima is set to offer Nomura the job after the regular season. If he takes it, he will become the youngest of 12 Japanese baseball club managers at 43.
Nomura ranks 34th on the all-time hits list in Japan with 2,020.
He was a .285 career hitter with 169 homers, 765 RBIs and 250 stolen bases in 17 years through 2005, all with Hiroshima.
Under Brown, the Carp have finished fifth, fifth and fourth in the past three seasons.