Harris was optioned to Triple-A Rochester on Saturday, Jesse Dougherty of The Washington Post reports.
Harris, who turns 30 in June, made a big-league roster for the first time when he cracked the Nationals' Opening Day roster, but he hasn't impressed during his time with the team. In 18.1 innings, he's struck out nine batters and walked 12 while struggling to a 5.40 ERA and 1.80 WHIP. Chad Kuhl (foot) was activated from the injured list in a corresponding move.