"It wouldn't surprise me," said Dodgers manager Joe Torre when asked if Ramirez could miss this weekend's series at Washington.
Ramirez singled to center off Reds starter Mike Leake to begin the sixth, but appeared to begin favoring his right leg halfway up the line. He was escorted off the field moments later by Dodgers assistant athletic trainer Todd Tomczyk.
Reed Johnson pinch-ran for Ramirez and remained in the game in left field.
Ramirez returned to the Dodgers' lineup on Tuesday after missing two games with tightness in his right calf. Torre fears this latest injury could be worse.
"He tweaked it more than the last time," said Torre.
Ramirez would not comment on the injury when initially asked by reporters after the game.
Entering Thursday night's action, Ramirez ranked second in the National League with a .421 batting average. He collected two RBIs in Wednesday night's game to give him 1,800 for his career.