The Nationals designated Eder for assignment Saturday, Danielle Allentuck of TheBaltimoreBanner.com reports.
Eder will forfeit his place on Washington's 40-man roster in order to make room for Curtis Mead, who was acquired in a trade with the White Sox on Saturday. Eder posted a 4.91 ERA and 1.31 WHIP over 18.1 innings with the Angels last season but found less success in Triple-A, where he ended the year with a 6.59 ERA across 68.1 frames (15 starts).