According to Yahoo Sports' Jeff Passan, who also reported that Miller is leaving the Reds, Miller's departure is part of an "overhaul," with more changes coming to the front office.
Miller was originally hired by the Reds in 2006 as director of baseball administration.
The Reds ended the season 76-86, finishing in fourth place in the National League Central and missing the playoffs for the first time since 2011. Cincinnati finished with its worst record since 2008.
The team announced Saturday that it has given general manager Walt Jocketty a two-year contract extension. Jocketty, whose contract was set to expire after this season, became the team's GM in 2008 and helped lead the Reds back to the playoffs in 2010 for the first time since 1995.
Jocketty had faced some questions about his job performance after failing to make any significant additions at the 2013 trade deadline, last offseason and this season's trade deadline. With first baseman Joey Votto injured for much of the year and outfielder Jay Bruce having a down season, Cincinnati finished 28th in MLB in runs scored in 2014.
It's unclear if the reported forthcoming front office changes are being directed by Jocketty or team owner Bob Castellini.
- Ben Estes