To make room for both players, Henry Rodriguez was transferred to the 60-day disabled list. Rodriguez underwent surgery on Friday to clean up a bone spur in his right elbow.
Duke, 29, is a seven-year veteran left-hander who was an All-Star starter for the Pirates in 2009. But after being dropped by the Astros in Spring Training -- the team with baseball's worst record last year -- Duke's prospects for returning to the big leagues seemed slim.
"Obviously you're always hopeful about going back to the big leagues, but the way that my Spring Training went and the last year went, getting released in Spring Training, the whole thing was just trying to get back to where I felt like I was the pitcher I was a capable of being, regardless of what the numbers and everything else was," Duke said. "So I feel like I was able to accomplish that, and this is just icing on the cake for me. I feel as good on the mound right now as I have in years. It's a very comforting feeling for a pitcher."
Duke, who is 48-74 with a 4.56 ERA in 181 games (168 starts) in his big league career, expects to pitch out of the bullpen, which he did for the second-half of last season while with Arizona.
Garcia, meanwhile, is on a Major League roster for the first time in his career. The 27-year-old right-hander has undergone two Tommy John surgeries to his pitching elbow after he was a third-round Draft pick by the Yankees in 2004.
Garcia signed with the Nationals last season, spending 2011 with Class A Auburn and Syracuse. He started this season in Double-A Harrisburg before moving up to Syracuse. In total, Garcia went 2-1 with a 0.86 ERA, 66 strikeouts and 17 walks in 52 1/3 innings in the Minors.
"To be with guys as talented as everybody in here is an honor, just to be able to put a jersey on," Garcia said. "Knowing that they're in first place and trying to clinch a playoff spot in the NL, just being here is an honor. Hopefully whatever I can do to help will be awesome."