While the move has been anticipated, a final decision won't be known until after Jennings meets with president of baseball operations Michael Hill, team president David Samson and team owner Jeffrey Loria.
While Jennings is likely to return to his general manager post, his name has been linked to the vacated GM opening in Seattle, an organization he once worked for.
The Marlins have been one of the major disappointments in the game. After making several high-profile offseason acquisitions, the club is now 54-79, a half game behind the Braves for third place in the National League East.
The Marlins are bracing to make sweeping organizational changes at all levels. On Tuesday, a source said, Marty Scott was reassigned from his vice president of player development role. Also, Craig Weissmann has been reassigned from his duties as vice president of player personnel.
Stan Meek, vice president of scouting, was given a contract extension through 2017. Meek oversees the Draft.
The Marlins also are evaluating their scouts, and changes are expected.
Jennings, who took over the Marlins when they were 16-22, has 31 years of professional experience in player development. However, he never coached or managed in pro ball before moving into the dugout with the Marlins.
For next season, the Marlins are expected to make a push for an experienced manager, and Don Mattingly could draw interest if he doesn't return as manager of the Dodgers. Larry Bowa, the Phillies bench coach, is another possibility. But those two aren't the only names being considered.
Joe Frisaro is a reporter for MLB.com. He writes a blog, called The Fish Pond. Follow him on Twitter @JoeFrisaro and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.