Peters, named on Thursday to the Arizona Fall League preliminary roster, is 6-2 with a 1.97 ERA in nine starts with the Jumbo Shrimp. He will likely join the rotation. From Triple-A New Orleans, right-handers Severino Gonzalez and Javy Guerra are bullpen possibilities for September.
"I do anticipate some moves," Marlins manager Don Mattingly said. "I'm not sure exactly what that's going to be at this point, if they are going to be staggered at all."
Peters and Guerra are not on the 40-man roster, but Gonzalez is.
The Marlins are not likely to add many position players. One possibility is Jacksonville outfielder Braxton Lee, who could provide speed off the bench and is a plus defender.
Miami's primary need for the final weeks, however, is pitching depth.
"It benefits you because there are going to be times when you don't want to have to use any of your bullpen pieces," Mattingly said.
Monday's 11-2 loss to the Nationals is an example. When the game got out of hand early, Mattingly stayed away from using his main setup relievers, not wanting to put more wear and tear on them.
The Marlins still could be open to making a trade, although they are not likely to add a starting pitcher.
One bullpen possibility is right-hander Juan Nicasio, who has already cleared waivers with the Pirates.