"Claude reported not feeling very good today," Holmgren's said in a statement. "Over the past few days, his symptoms have gradually gotten worse. He will be out indefinitely with a concussion."
That statement is a change from Monday, when Holmgren said Giroux "is continuing to feel better" and would see a team doctor instead of traveling to Washington.
The 23-year-old notched two assists before departing, to boost his NHL-leading point total to 39.