Like Werth, outfielder Jeff Kobemus, sidelined by flu-like symptoms, did not travel with the Nationals to face the Braves on Tuesday.
"Kobemus is still feeling it, so we left him back today," Williams said. "He has a little stomach issue, so he's not feeling well."
Outfielder Bryce Harper experienced similar stomach issues on his scheduled off-day on Sunday, but started in left field and batted third in Tuesday's game.
Joe Morgan is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.