In a corresponding move, Koyie Hill had his contract selected from Triple-A New Orleans. Hill, 34, has previous big league experience, appearing in 313 games over nine seasons. In 2012, he appeared in 11 games with the Cubs.
Brantly, 23, has had his share of struggles, at the plate and in the field. He is batting .225 with one home run and 18 RBIs in 59 games. In the field, he has seven passed balls and a fielding percentage of .989.
The Marlins have been weighing for a while how to best address Brantly's situation.
"We talked about it, and I felt like it was best for him to go down to the Minor Leagues and get a chance to play these next 25, 26 games, whatever left down there," manager Mike Redmond said. "I really was only using him one or two days a week, max. I just felt like in the development process, it was best for him to go down and play and work on parts of his game that he needs to work on and get some confidence. I think it will be really good for him."
At New Orleans, Brantly will have a chance to work on his game-calling, as well as all phases of his game.
"Part of what concerned me is he may have lost his personality a little bit," Redmond said. "We saw a guy in Spring Training who was bouncing around, having fun, joking around. Then over the last, really, a month, I think he kind of lost that. For me, it's confidence. The big leagues is tough. You've got to have your game right."
For a few months, Brantly's playing time was reduced as Jeff Mathis handled a majority of the catching duties. The veteran Mathis has regularly been behind the plate for rookie phenom Jose Fernandez.
Brantly's most recent start was on Wednesday at Pittsburgh. He was hitless in three at-bats. Prior to then, he hadn't started since last Saturday in a loss to the Indians.
Miami acquired Brantly, along with Jacob Turner and Brian Flynn, from the Tigers on July 23, 2012, for Anibal Sanchez and Omar Infante.
A left-handed hitter, Brantly is a career .280 hitter in the Minor Leagues.
By being sent to Triple-A, Brantly will get a chance to play every day and refine his skills in the field and at the plate.
The Marlins promoted Brantly late last season, and in 31 games and 100 at-bats, he batted .290.
Hill provides a veteran backup presence to Mathis. With New Orleans, he batted .237 with one homer and 14 RBIs.
"With young prospects, sometimes you've got to take a step back to get them back on track," general manager Michael Hill said of Brantly. "We will get him back in the flow, and hopefully, he regains some confidence."
How Brantly performs at New Orleans could determine if he rejoins the Marlins in September.
"There was never any pressure put on him," Hill said. "Given our season, we knew we were going to have some challenges with some young players, and to see if they make progress and continue to get better. We've always said, if we felt they had lost confidence, it was time for them to go back and right the ship. That's sort of where we're at."