The Diamondbacks have informed Littell that he'll work out of the bullpen, Alex Weiner of ArizonaSports.com reports.
Littell signed a one-year contract with Arizona on Sunday, and the team intends to use him in a relief role to begin his D-Backs tenure. He's appeared as a reliever in nine of 23 appearances this season with Washington, and he stated in an interview Monday that he's willing to do whatever he can to help his new club. Littell most recently worked 6.2 innings Tuesday in his final appearance before being designated for assignment by the Nationals, so he's in a position to step into a starting role in the event of an injury.