Craig Kimbrel
Expected to enter the season competing for the primary setup role to closer Craig Kimbrel, Simmons received unfortunate news when an MRI revealed a tear to his UCL in his throwing elbow, causing him to miss the entire 2015 season. On February 12, 2015, Simmons underwent successful Tommy John surgery, performed by Dr. James Andrews. He began pitching again in May 2016, but recovery was slow, as he was affected by other minor injuries. The Braves recalled Simmons on August 30.