To make room on the roster for Cedeno before Friday's game against the St. Louis Cardinals, the Nationals optioned righty reliever Blake Treinen to Syracuse.
Treinen allowed one earned run in 6 2-3 innings since making his major league debut last weekend.
Cedeno has pitched 3 2-3 scoreless innings for Syracuse this season. He has a 5.40 ERA in 45 innings in the majors, including 11 games with Washington last season. The Nationals acquired him from the Houston Astros in a trade in April 2013.