Littell agreed to a one-year contract with the Diamondbacks on Sunday, Nick Piecoro of The Arizona Republic reports.
The veteran right-hander was let go by the Nationals on Friday after posting a 4.97 ERA, 1.34 WHIP and 70:35 K:BB across 112.1 innings on the season. Arizona's rotation depth has been thinned out in recent weeks, but with Michael Soroka (glute) poised to come off the injured list Monday, the Diamondbacks may not have a spot available for Littell. With that in mind, Littell could have to settle for a long-relief role to begin his time in Arizona.