The Red Sox led the Tampa Bay Rays by nine games for the final American League playoff spot in September before the club finished 7-20 in the last month to miss the postseason by a game.
Francona leaves the Red Sox, his second managerial position, with a 744-552 record and two World Series championships in 2004 and 2007. He went to the playoffs five times in his eight years at the helm.
"(Francona) said that after eight years here he was frustrated by his difficulty making an impact with the players, that a different voice was needed and that it was time for him to move on," the Red Sox ownership group said in a statement.
MORE TO FOLLOW.