The Swedish midfielder continues to suffer from head problems and has been forced to miss some games in recent times.
Sounders coach Sigi Schmid confirmed the former Arsenal man would sit out the Revolution match.
"Right now, (we are) keeping him out of the game tomorrow, progressing him slowly forward," Schmid told reporters after Wednesday's training.
"We want to make sure there is not a recurrence. It wasn't a migraine. We are sure of that.
"But right now, we are just following a very precautious procedure. So they felt the 7-10 day protocol was the right thing to follow and that is what we are following right now."
Schmid said all tests were negative, so doctors believe Ljungberg's problem might be related to diet and travel strains.