The Guardians traded Hartle, Will Dion, Kendeglys Virguez and Nick Mitchell to the Nationals on Monday in exchange for Foster Griffin, Mark Feinsand of MLB.com reports.
A 23-year-old southpaw, Hartle has a 3.86 ERA, 1.38 WHIP and 88 strikeouts in 93.1 innings at Double-A. He projects as either a back-end starter or middle reliever.