While the callups have not been finalized, a source said that Danny Espinosa will likely not be among them. The source also said that Triple-A shortstop Zach Walters will be called up.
When asked about Walters, who is the Nationals' No. 12 prospect and leads the International League with 29 home runs, Johnson chose his words carefully.
"He's certainly deserving, let's put it that way," Johnson said. "And I would like to see him come up."
Johnson said that each of the callups have played for him before, either with the Nationals or during Spring Training. He only confirmed that one player will definitely rejoin the team: left-hander Ian Krol.
Outfielders Corey Brown and Jeff Kobernus and left-handed reliever Xavier Cedeno are also safe bets to be called up.
Tom Schad is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.