The Nationals swapped relievers prior to Tuesday night's series opener against the Marlins, recalling right-hander Ryan Mattheus from Class AAA and optioning lefty Xavier Cedeno back to Syracuse.
Mattheus had only been demoted to the minors 12 days ago after struggling upon his return from a broken hand. But he allowed only one run and six hits in 7 1/3 innings at Syracuse, including three straight scoreless appearances to end his brief stint there.
A key member of one of baseball's deepest bullpens in 2012, Mattheus has a 6.26 ERA in 23 games with the Nationals, interrupted by a two-month stint on the disabled list with a broken right hand suffered when he punched his locker in San Diego following a rough outing.
Cedeno had only been called up on Friday following the trade of outfielder David DeJesus. The lefty has been promoted and demoted four separate times this season yet has appeared in only two games, allowing one hit in 1 1/3 innings.