Atlanta didn't officially rule Simmons out for the season, but general manager Frank Wren and manager Fredi Gonzalez acknowledged that the time has likely run out for him to return.
Simmons, who turned 24 on Wednesday, made two rehab appearances for Triple-A Gwinnett last month but was shut down on Aug. 20 with what he called an "extremely sore shoulder."
"There is no reason to push him," Gonzalez said before the Braves' game in Miami on Friday.
Simmons is 1-2 with a 2.91 ERA and one save in 26 appearances this season.
Atlanta entered play tied for the NL's second wild card spot with Milwaukee at 73-67.
- Chris Mascaro