DeRosa, a veteran utility man hitting .152, has been on the disabled list since Aug. 5 with a groin injury. Despite his offensive struggles, DeRosa is considered a valuable veteran presence, was a World Series champion in 2010 with the San Francisco Giants and adds flexibility with his ability to play the outfield and middle infield.

Johnson didn’t speculate on who the players would be. But potential catching candidates include Sandy Leon and Jhonatan Solano, who both played in at least 10 games this season, filling in for other injured catchers. Leon, known as a solid defender, is in Syracuse hitting .378. Solano is in Class AA Harrisburg, hitting .250, rehabbing an oblique injury that landed him on the disabled list on July 18.

Potential candidates for the pinch-running role include Corey Brown, a Class AAA Syracuse outfielder with power spent time with the Nationals this season, and Eury Perez, a Syracuse outfielder who has stolen 50 bases across three minor league levels this season.

“The only really important couple guys, DeRosa will be activated and I would probably call up another catcher,” Johnson said. “It frees up another bat and maybe a pinch runner. Those are really the only three critical ones when we expand rosters.

John Lannan, a fixture in the Nationals’ rotation over the past four seasons but optioned to Class AAA Syracuse before opening day to make room for Ross Detwiler, won’t be called up immediately, Johnson said. He will likely make one more starter for Syracuse before he is added to the Nationals rotation upon the impending shutdown of Stephen Strasburg.

“I think it’s going to pretty much coincide fairly close with Stephen, when he’s shut down. I think the timing, he’s lined up almost the same day so he may have to miss a start. I probably won’t have him come out of the ‘pen. I’ll probably just have him do side work and maybe even throw a little sim game.”

Lannan tossed a three-hit shutout on Saturday and earned International League player of the week honors. His start on Saturday came on six days rest. Johnson suggested that Lannan could pitch on the Syracuse’s final day of the season, which is September 3.

“He’s a great pitcher,” Johnson said. “He pitched two great ballgames for us up here and nice to see he’s throwing well. He’s used the time to work on some things. I’m sure he’s in a good frame of mind and it couldn’t come at a better time.”

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