"A tough decision, because, to be honest with you, it could be either one," manager Ozzie Guillen said. "That is a message for another player. It could be either one."
Following Thursday's game, Guillen met for 45 minutes with members in the front office.
Guillen didn't speak with the media following the game because the meeting took a while. But the manager made it clear that several other players should be aware that more is expected.
"The reason I didn't talk to the media yesterday is because there were like seven names involved in the meeting," Guillen said. "We had to pick one. Unfortunately, it was Petey. I think the team is better than we are right now."
Petersen was hitting .212 while getting steady playing time in center field.
Miami made a position-player move to make room for outfielder Austin Kearns, who was reinstated from the disabled list, where he had been out with a strained right hamstring.
"It's a warning," Guillen said. "The meeting was 45 minutes for one player. That means there were a few players involved in the meeting. They better step it up.
"In case, if they don't know, be aware. You never know what's going to happen. They better look themselves in the mirror and say, 'Why Petey and not me?' It took a little while to make this move. Believe me."
The Marlins also optioned lefty reliever Dan Jennings to New Orleans, and on Friday they recalled right-hander Sandy Rosario.
Miami has one lefty in the bullpen now, Randy Choate. Edward Mujica is an option to face left-handed hitters.