Prior to Tuesday's game at the Verizon Center against the Washington Capitals, Holmgren expanded on the situation.
"Over last few days his symptoms have gotten worse," Holmgren said. "He skated a little bit [Tuesday] and didn't feel that good, like himself."
The Flyers had said on Monday that Giroux was making progress. Holmgren said originally it appeared as if Giroux didn't have a concussion.
"He didn't have concussion symptoms right away," Holmgren said. "It was more whiplash and discomfort in the next."
All that would change.
"As the last few days have transpired, it became more and more that he didn't feel like himself, was sluggish and that is the reason we are doing this," Holmgren said.
Giroux skated both Monday and Tuesday, according to Holmgren.
"I don't know if it is any good news, but after 15 minutes or so once he stopped skating [on Tuesday], he did start to feel better," Holmgren said. "But we're going to take it easy with Claude."
Holmgren said they would keep him off the ice on Wednesday and possibly revisit things on Thursday. So much has to do with how Giroux feels each day. The Flyers general manager also said that the team may have to use some tough love.
"He is a stubborn guy and wants to go out there," Holmgren said.
That will only happen when he feels like his old self, according to Holmgren.
For now, Giroux won't be seeing outside doctors the way defenseman Chris Pronger is for his concussion-like symptoms. Pronger will meet with two Pittsburgh concussion specialists on Wednesday.
"Right now we are not going to go that route," Holmgrens said. "We're going to stick with our doctors. "Chris is a little different issue and Claude will stick with our doctors."
Giroux didn't undergo baseline testing on Tuesday, but he had on Monday
"He did it [Monday] and it was not bad," Holmgren said.
The Flyers have weathered so many key injuries and entered Tuesday as the top team in the Eastern Conference with 39 points.
Still, seeing a player who has been listed as a major Hart Trophy candidate as MVP leave the ice, the Flyers understandably were concerned following their morning skate.
"He's a guy that you can't really replace," forward James van Riemsdyk. "It will take a lot of people to step it up and try to fill the role he plays."
It is certainly an expanded role.
"He does everything for us, penalty kill, power play, scores big goals, takes big hits, blocks shots, he does it all," van Riemsdyk said. "So we will all kind of have to step up our game here."
Knowing how dominant Giroux has been made his situation even more difficult for his teammates to cope with.
"You don't want to see anybody go down, especially our best player," said Giroux linemate Scott Hartnell. "When he is in the lineup and doing his thing, we are obviously a very dangerous team."
Getting accustomed to key injuries has become a way of life for the Flyers.
"Things like this happen," Hartnell said. "You want him to get healthy and feel better and get back in the lineup."
Contact staff writer Marc Narducci at 856-779-3225, firstname.lastname@example.org, or @sjnard on Twitter.