Nathan posted a 3.86 ERA in 12 spring appearances for the Nationals as he attempts to fully return from a second Tommy John surgery. The 42-year-old signed a minor league contract with the Nationals in January and Monday was the deadline for him to exercise an opt-out clause.
"There's 29 other teams," Nathan told reporters. "I knew every time I took the mound this spring, it wasn't just to try to make this club but showcase for other teams. It was important for me to get out there, even yesterday, in a spot where they probably already knew I wasn't going to make this team."
Nathan pitched 6 1/3 innings with the San Francisco Giants and Chicago Cubs last season. He underwent surgery in April 2015 after throwing only four pitches with the Detroit Tigers and also underwent the procedure in 2010.
Nathan is eighth all time with 377 saves. He has four seasons with at least 40 saves and in his last full season Nathan had 35 saves and a 4.81 ERA in 62 appearances with Detroit.
Nathan began his career as a starting pitcher with the Giants in 1999. After spending 2001 in the minors, he was moved to the bullpen and began closing games in 2004 with the Minnesota Twins.
Washington also released Matt Albers, who made 10 scoreless appearances during spring training. Albers signed a minor league deal with the team in January after posting a 6.31 ERA in 58 appearances for the Chicago White Sox last season.