Right-handed reliever Juan Jaime was recalled from Triple-A Gwinnett to fill the vacant roster spot.
"We're just going to back off [Simmons] for a little bit," Braves manager Fredi Gonzalez said. "He won't throw for a few days and then we'll see where he's at. I don't expect him to be [sidelined] after 15 days, or not much longer after that."
Simmons, who accompanied the Braves to Los Angeles, said he has been experiencing some tightness around his right shoulder for about a month. But the rookie did not inform the Braves until he completed his latest shaky appearance on Saturday, when he walked two of the three Padres he faced.
"It's just more tight than anything, so I felt real limited on my movement, especially coming back [with my arm during my delivery]," Simmons said. "But we're working on it, and it's starting to feel better already. So things are looking up."
Simmons has surrendered five earned runs and allowed opponents to compile a .419 on-base percentage during the six innings he has completed dating back to July 7. Eight of the past 13 batters he has faced have reached base with a hit or a walk.
In other words, Simmons has not been nearly as impressive as he was when he earned the nickname "Baby Kimbrel." During the 18 appearances he made before hitting this rough patch, he posted a 1.15 ERA and limited opponents to a .228 on-base percentage. Simmons recorded 15 strikeouts and issued just three walks in 15 2/3 innings during that span.
While the shoulder might have influenced Simmons' struggles, Gonzalez said he believes Simmons was also experiencing some growing pains that he initially avoided after making the jump from Double-A Mississippi on May 31.
"With his stuff at Double-A, he eliminates seven hitters in a good lineup," Gonzalez said. "When he gets to the big leagues, he's going to have to work a little harder and also on back-to-back days in the Major Leagues with high-intensity innings. I think it's just a matter of growing."
Jaime impressed during his only previous Major League stint. In the four innings he completed for the Braves from June 20-26, the hard-throwing right-hander allowed one hit and one run. More importantly, Jaime showed good command as he struck out seven and issued just one walk.
After being sent back to Gwinnett, Jaime has again suffered from command problems that have long kept him in the Minors. The 26-year-old reliever allowed eight earned runs while issuing 10 walks and striking out eight in six innings form June 30-July 19. But Jaime has since made three consecutive scoreless appearances, during which he has recorded seven strikeouts and issued three walks -- all of which were tallied in one game.