The Guardians traded Dion, Josh Hartle, Kendeglys Virguez and Nick Mitchell to the Nationals on Monday in exchange for Foster Griffin, Mark Feinsand of MLB.com reports.
Dion, a 5-foot-10 southpaw, has a 4.58 ERA in 19.2 innings this year out of the big-league bullpen, but his fielding-independent metrics are quite a bit better (2.53 SIERA) thanks to a 29.4 percent strikeout rate and 3.5 percent walk rate. He was optioned to Triple-A on Sunday but could quickly join the Nationals at the big-league level.