PITTSBURGH -- It is both sobering and instructional to realize how quickly we have gone from anticipation to resignation when it comes to the troubling case of Sidney Crosby.
It is a stark reminder of where the NHL is at with its epidemic of serious head injuries to top-line players that in the blink of an eye we have morphed from marveling at Crosby's dramatic return to action to acting as if he has vanished from the earth.
One minute, Crosby is streaking down the ice against the hapless New York Islanders en route to a seminal four-point performance after more than 10 months of rehabbing, and the next, poof.
Gone. Disappeared. Down the rabbit hole.
On Wednesday, the team prepared for what will be an emotional tilt on Thursday night against the Philadelphia Flyers, former Pittsburgh Stanley Cup hero Max Talbot and five-time NHL scoring champion with the Penguins Jaromir Jagr.
Crosby remained conspicuous by his absence, but after days of non-reports regarding his status, Penguins head coach Dan Bylsma confirmed after practice that the team's captain was experiencing more concussion symptoms.
"Sidney Crosby is light exercise at this point and still having some symptoms," Bylsma said.
And that was it.
On our trip into Pittsburgh, we got to thinking about the moments we have intersected with Crosby.
We were at his first NHL game in New Jersey in 2005.
We were at the NHL awards ceremony that spring where he was bested by arch nemesis Alex Ovechkin for Rookie of the Year honors.
We saw every Penguins playoff game between 2007 and their Cup win in 2009.
We followed Crosby's days with the Cup in Cole Harbour, Nova Scotia, including a rare visit to Crosby's lakefront home outside Halifax.
We saw Crosby score a goal for the ages in overtime to give Canada a gold medal against the Americans at the 2010 Olympics in Vancouver.
We have seen him meet virtually every expectation put upon him, no matter how unrealistic, with unwavering good grace and humility.
Perhaps what is most curious, even eerie, is that now there seems to be almost no expectation for Crosby.
In the 361 days since Crosby was first stunned by a glancing blow to the head by David Steckel in the Winter Classic, there was a palpable buzz that surrounded his rehabilitation. Even when there was nothing to say, there was no shortage of discussion about what wasn't being said.
There was the late-summer press conference in Pittsburgh with doctors who insisted -- erroneously, as it turned out -- that once Crosby came back at 100 percent he would play as though he'd never had a concussion.
While Crosby did play at a level that defied the time spent away from the game, it appears a rather innocuous hit by David Krejci of the Boston Bruins -- if it was that hit at all -- has reinforced the spectral, almost supernatural quality of concussions and their unpredictability.
At the beginning of training camp, we watched Crosby practice at a high level from the moment the Zamboni left the ice at Consol Energy Center, ramping up the expectations about his imminent return.
And when he came back, it seemed every precaution taken was justified by Crosby's level of play. He registered 12 points in eight games beginning on Nov. 21. (His last game was Dec. 5 against the Bruins.)
But in the end, he proved what many had wondered about, fretted over during his rehabilitation: the idea that regardless of the precautions, the next hit, no matter how innocuous, how ordinary, could be "the one."
Ask Philadelphia captain Chris Pronger.
Is anyone entirely sure just what it was, other than two decades of pounding and grinding at the highest level, that sent Pronger down a similar rabbit hole shortly before Christmas?
The Flyers took the unusual step of announcing that Pronger would not return this season, nor would he be available for the playoffs.
This decision was reached after spending time with some of the concussions experts that treated Crosby. Which leads inexorably to the question about whether the Pens are considering something similarly emphatic when it comes to Crosby?
A source familiar with the Crosby situation told ESPN.com Wednesday there has been no thought given to taking that kind of drastic action.
The team and doctors will continue to monitor how Crosby feels and that will be their guide, as it has been from the outset as to when or if he returns.
And here's the thing: Just as the Flyers were closing the book on Pronger's season, his teammate, NHL scoring leader Claude Giroux suffered a concussion after being kneed in the head by teammate Wayne Simmonds. Yet there he was shortly before the holiday break, returning unexpectedly to record four points a la Crosby in a win over Dallas.
Norris Trophy nominee Shea Weber of the Nashville Predators was also diagnosed with a concussion this week, but immediately head coach Barry Trotz was talking about Weber's possible return this Friday.
In both Philadelphia and Nashville, the worry watch will no doubt continue for those players; the wondering and fretting about when or if the rabbit hole awaits their star players as well.
Still, Giroux's return juxtaposed against the discomforting absences of Pronger and Crosby merely reinforces that the distance between anticipation and resignation may be achingly short but is among the toughest roads that criss-cross the sport.
Scott Burnside covers the NHL for ESPN.com.