With the moves, the Nationals currently have 36 players in big league camp.
Duncan, who signed a Minor League contract this past offseason, played in 12 exhibition games for Washington and was 5-for-32 (.156) with seven RBIs. He believes he is close to being the hitter that hit .293 with 22 home runs and 43 RBIs with the Cardinals in 2006.
The past two years, Duncan lost his swing, hitting a combined 11 homers because of injuries.
"If I can go down there, get at-bats and find my swing, the Nationals could find a spot for me on this team," Duncan said. "I don't think I found my swing yet. I'm a lot closer than I was last year. I put in a lot of work. Hopefully it comes around. I know what I'm capable of when I get hot."
Martis was hit hard, giving up eight runs in 5 1/3 innings. He was told by pitching coach Steve McCatty to improve his mechanics. If he returns to the Majors, Martis could work out of the bullpen.
"McCatty talked about a more consistent release point," manager Jim Riggleman said. "Martis just needs to progress. As much as anything, the numbers don't allow him to be with us right now. I'm confident that not only can he come up here and start, but pitch out of the bullpen."
Orr was fighting to be a backup in the big leagues, but he went 4-for-20 (.200) with no RBIs. Riggleman felt Orr put too much pressure on himself.
"We are very confident that Pete could help us," Riggleman said. "Pete is a good player. I don't think Pete showed his best here. I think he will be the first to tell you that. In trying to win a job, he didn't let himself relax and be the player he could be."
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.