The Nationals have secured outright waivers on right-hander Joe Bisenius, who has elected to become a free agent.
The 28-year-old Bisenius posted a 9.64 ERA in five outings with the Nationals in 2010, his first major league action since a cup of coffee with Philadelphia in 2007. He struck out five and walked six in 4 2/3 innings.
However, at three minor league levels of the Nationals organization last season - with Single-A Potomac, Double-A Harrisburg and Triple-A Syracuse - Bisenius was 4-0 with a 3.05 ERA in 34 relief outings.
The Nationals' 40-man roster now contains 38 players.