After joining the Reds as an assistant trainer in 1995, Mann assumed the role of head trainer in 2003. He had served in that capacity up until now.
Mann has accepted a job with Morgan Stanley Smith Barney, where he will become licensed as a financial adviser and then assist the firm in its accounts with former and current Major League players.
"They felt like I was a very good conduit to future business," Mann said of the opportunity, which will also afford him more time to spend with his wife, Michele, and their two sons. "They brought me here because of my relationships in baseball."
Jocketty has already begun the search to replace Mann and will head the interview process. Mann has offered to help Jocketty in that process as much as possible through the end of the calendar year.
"It's one of those things where I told him I want this to be seamless," Mann said. "I'll do everything I can to help the Reds with the transition. I will be involved in that process. I've got a lot invested with the Reds and I just want to see that through."
Mann also emphasized that his decision to leave the organization was in no way connected to his mother's retirement from the club late last week. Wilma Mann served as the Reds' director of scouting administration for 37 years before recently retiring from the post.
"It's just very ironic that everything just broke down within 24 hours of each other," Mann said. "I actually informed Walt of my decision to resign the day before my mom announced that she was retiring. They have nothing to do with each other."
Jenifer Langosch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.