Johnson said the Nationals will activate injured utility man Mark DeRosa on Saturday, promote a third catcher to free up another bat off the bench and maybe add a player to use as a pinch-runner.
"Those are really the only three critical ones when we expand rosters," Johnson said. "Those three for sure right away."
DeRosa has been on the disabled list since Aug. 6 with a left abdominal strain, although he has remained with the team. The Nats have two main options at catcher to back up Kurt Suzuki and Jesus Flores: Sandy Leon and Jhonathan Solano. Leon is with Triple-A Syracuse, while Solano (left oblique strain) is on a rehab assignment with Double-A Harrisburg.
Johnson did not mention injured pitchers Henry Rodriguez (lower back strain) or Chien-Ming Wang (hip strain) when discussing players who will join the club immediately after the rosters are expanded.