Littell was optioned to Triple-A Sacramento on Friday, Maria I. Guardado of MLB.com reports.
Littell pitched Thursday against Atlanta and allowed one run over three innings, and he'll head to the minors in favor of a fresh bullpen arm. The 26-year-old has a 4.97 ERA, 1.17 WHIP and 25:3 K:BB across 29 major-league innings this season.