The team needs bullpen help because closer Matt Capps and setup man Tyler Clippard have been used often and the rest of the relievers in the bullpen, with the exception of left-hander Sean Burnett, have struggled this season.
Slaten, who was drafted by the D-backs in the 2000 First-Year Player Draft when Nationals general manager Mike Rizzo was in the Arizona organization, was outstanding for Syracuse, allowing no runs in 17 innings.
With Slaten in the fold, this would give Burnett a chance to face all hitters instead of being a lefty specialist. The Nationals are considering making Burnett the seventh-inning reliever, replacing Brian Bruney.
As for Chico, he replaced left-hander John Lannan for one start on Saturday because Lannan had elbow discomfort. Chico hadn't pitched in a Major League game since May 21, 2008, after undergoing Tommy John surgery on his left elbow.
Chico tossed five scoreless innings before the Marlins opened the sixth inning by stringing together three successive hits, Jorge Cantu's double down the left-field line getting Florida within two at 3-1.
Chico's first pitch of the afternoon hit Cameron Maybin on the back foot, an inauspicious start that was quickly overcome. Chico got through his outing having allowed just two runs on six hits in five-plus innings. He walked none and struck out three.
"That first pitch, all the nerves started coming back," Chico said. "It felt like my first big league game again. I just tried to brush it back and go after the next guy. After that, it was, 'Let's go at 'em and just try to get a ground ball.'"
Bill Ladson is a reporter for MLB.com. Pete Kerzel contributed to this report. This story was not subject to the approval of Major League Baseball or its clubs.