Johnson hurt the shin in the first inning when he was hit by a John Smoltz pitch. Johnson stayed in the game long enough to score the first run of the game on Josh Willingham's RBI single, but it was obvious that he had difficulty running the bases.
Johnson will be reevaluated on Friday before the Nationals play the Orioles at Camden Yards.
"The shin swelled up, and then when he was running the bases, he was very uncomfortable," manager Manny Acta said.
Johnson was unavailable for comment following the game.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.