The Toronto Maple Leafs didn't have a chance to follow any of the guidelines set out in the NHL's concussion protocol because they were unaware the forward was even experiencing symptoms until almost 48 hours after the collision that caused them.
Armstrong was injured during Saturday night's game against Vancouver but didn't let the team's medical staff know he was feeling nauseous until Monday afternoon.
"It took us all by complete shock because we had no idea that he had his bell rung the other night," Leafs coach Ron Wilson said after Monday's 3-2 shootout loss to Los Angeles. "He kind of kept that from us."
In fact, Armstrong told reporters on Monday morning that he expected to play against the Kings despite a minor foot injury. Now he'll be sidelined indefinitely with something much more serious.
Wilson offered a surprisingly frank recap of how the situation played out.
"Well here's what happened," he said. "In the game the other night, (Armstrong) hit Ryan Kesler and actually he cracked his toe, but that wasn't an issue. He didn't tell the trainers or the doctors yesterday that he had his bell rung. (This afternoon) he was nauseated, blurry vision, so he's got a concussion and we didn't know that until later in the afternoon.
"He's going to be out however long he needs to be out now."
The 29-year-old winger has missed time with a variety of ailments over the last year and a half, playing just nine games for the Maple Leafs this season. Wilson hinted that that may have played a role in his attempt to hide the concussion.
"Things have been going so badly for him with injuries," said the coach.
It comes at a time when the concussion debate is raging again in hockey circles with a number of high-profile players on the sidelines. Philadelphia Flyers captain Chris Pronger is already done for the season while the likes of Sidney Crosby, Claude Giroux, Kris Letang, Marc Staal, Jeff Skinner and Milan Michalek remain out.
Last week, agent Allan Walsh told The Canadian Press he believes the NHL is in "the throes of a concussion epidemic" — a claim the NHL vehemently denied.
"I don't believe it's a crisis, I don't believe it's an epidemic," said deputy commissioner Bill Daly. "There's nothing we can do that doesn't change the game fundamentally that's going to eliminate concussions in our game. Bottom line is they're a fact of life in a contact sport — not just ours — and they continue to be a fact of life."
Unfortunately for Armstrong, his name has been added to the list of sufferers. Wilson indicated the player felt nauseous after riding a stationary bike on Sunday and got even more sick after participating in Monday's morning skate.
The team didn't even need to put him through a concussion test to diagnose his concussion.
"He's sick, threw up today and (has) a headache and blurry vision — you don't need an imPACT test at that point," said Wilson.