Dietrich is eligible for arbitration after making $2.9 million this year, when he hit .265 with 16 home runs in 149 games while playing mostly in left field. He's a .254 career hitter with 60 homers.
The move takes Dietrich off Miami's 40-man roster, opening a spot for one of seven minor leaguers who were added Tuesday to protect the team from next month's Rule 5 draft at the winter meetings. The Marlins have seven days to trade or release Dietrich or send him outright to the minors. Because he has three years of major league service, he could refuse an outright assignment and elect to become a free agent.
Dietrich's departure means All-Star catcher J.T. Realmuto has been with Miami longer than any other Marlins player.