Stephens was placed on the 15-day injured list Sunday, retroactive to Sept. 30, with right elbow inflammation, Justin Toscano of The Atlanta Journal-Constitution reports.
Stephens delivered two scoreless frames Friday against Washington, but an elbow issue apparently surfaced during the outing. The 29-year-old right-hander wasn't a strong bet to make Atlanta's NLDS roster even if healthy with just five big-league appearances this season, and he'll now be unavailable until at least mid-October.