Falter was optioned to Triple-A Lehigh Valley after starting Thursday's game against the Nationals.
Falter threw four innings while allowing two earned runs on six hits and a walk in a no-decision. He also struck out six, his highest mark in any outing in the majors this season. Falter will remain a candidate to work in long relief or make spot starts for the Phillies throughout the season, but for now he'll head back to the minors.