Miami dropped to 14-22 under Jennings with a loss to the Cardinals on Thursday night.
Miami's rookie manager has seen his club struggle with runners in scoring position and suffer from injuries to notable starting pitchers, but according to FOX Sports' Ken Rosenthal, league officials are beginning to wonder how Jennings would fare as the club's manager if the Marlins were in the postseason conversation after the All-Star break.
While the Marlins are hoping to get as close to five hundred as possible before the break, the squad has not performed any better under Jennings.