Nittoli was optioned to Triple-A Lehigh Valley on Sunday, Corey Seidman of NBC Sports Philadelphia reports.
Nittoli made two scoreless appearances after being called up Sept. 1, but the Phillies decided to remove him from the roster to open up a spot for fellow reliever Seranthony Dominguez. Nittoli will garner consideration if the Phillies need to bring up a reliever before the season comes to a close.