Dukes played left field, and he went 0-for-2 with two walks against the Class A Frederick Keys.
Unlike outfielder Wily Mo Pena, the Nationals are not going to rush Dukes back to the big leagues. General manager Jim Bowden said that Dukes has to start hitting before he's promoted.
In other news, reliever Ray King said by phone on Sunday that he did not demand that the Nationals trade him after he was optioned to Triple-A Columbus on Thursday. He just wanted to be placed on waivers so he wouldn't go back to the Minor Leagues.
The Nationals recalled King from Columbus on Saturday, but he will not report to the club.
The team then placed King on waivers. If he is not picked up by a Major League club by Tuesday, he can go back to Columbus. But King is expected to choose free agency instead.
Neither King nor Bowden would talk about the lefty's future.
When the Nationals optioned King to Columbus, they selected the contract of left-hander Mike O'Connor from Triple-A.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.