Pronger was feeling sluggish recently before the Flyers realized he may have a head injury. He will be seeing special doctors in Pittsburgh on December 14 for further evaluation.
Currently listed as "out indefinitely," the team may be in trouble if he is unable to return.
Chris Pronger won his Hart Trophy more than 10 seasons ago, but the 37-year-old is still one of the league's best defensemen.
He is without a doubt the Flyers' best defenseman when healthy.
On the offensive side, Pronger has 11 points in 13 games this season. Defensively, he's continued to play like a former James Norris Trophy winner, consistently shutting down the opposition's best players.
Pronger on the ice and on the bench is one of the game's most key role players.
The Flyers have additional leaders such as Danny Briere, Kimmo Timonen, Jaromir Jagr and Max Talbot, but none of them can bring the intangibles of Pronger.
Though the Flyers have managed to step up their play recently, winning the last five games, the team has always done better with Pronger.
With him, they have 41 wins and 25 total losses (including playoffs). Without him they have 28 wins and 27 total losses.
The Flyers currently have five players on the long term injury reserve. When a player is on the LTIR the team may use replacement players totaling a cap hit equal to or less than that of the players on the LTIR.
Even with Pronger's large salary essentially not counting at the moment, the Flyers have absolutely no cap space, according to CapGeek.com.
The Flyers are unable to add a replacement defenseman at the moment, leaving players like Marc-Andre Bourdon and Kevin Marshall in the lineup.
Depending on how serious this concussion is, the Flyers may be without Pronger throughout this season and possibly even next season.
Any long-time Flyers fan will remember Eric Lindros' recurring concussions; the former Flyers captain had five during his time in Philadelphia.
This news could be the beginning of the end for Pronger. Even if he does return healthy this season, the effects of a concussion always seem to find their way back.
Note the recent news regarding Sidney Crosby as an example. The young forward is currently missing games as a precautionary measure after missing much of last season and this season due to a head injury.
If the Flyers must see their way into next season without Pronger, his linemate's contract becomes even more of an issue.
It runs out this summer.
Having given a raise in pay to James van Riemsdyk, which will take effect in the 2012-13 season, the Flyers have little cap room to use for resigning Matt Carle.
Carle is one of the Flyers' core defensemen. If he leaves, Pronger's absence means the Flyers lose an entire line for next season.
Because Pronger signed his contract after the age of 35, his salary counts towards the Flyers cap even if he retires.
This rule of the NHL's Collective Bargaining Agreement is meant to stop teams from front-loading contracts for players nearing retirement.
Of course, if Pronger reaches a point where he decides playing is no longer an option, he could choose to unofficially retire (as Ian Laperriere essentially has), but be listed on the LTIR to help the Flyers.
With Carle's contract expiring and the potential of being without Pronger, the Flyers face questions regarding the team's future on defense.
Kimmo Timonen is 36 years old and his contract will run out after the 2012-13 season.
When that time comes, the Flyers may be left with Andrej Meszaros, Braydon Coburn, and an injured Pronger.
The Flyers undoubtedly had their eyes on the Stanley Cup when bringing Chris Pronger to Philadelphia before the 2009-10 season.
If Pronger's current head injuries spell out the deterioration and end of his career, the Flyers will not have spent their assets well.
Even if the Flyers manage to win a Stanley Cup without Pronger, having him in the press box means they did not get what they wanted out of the 2009 draft day trade.
Philadelphia gave Anaheim Joffrey Lupul, Luca Sbisa and two first-round picks for Pronger.
Two first-round picks are definitely more valuable than someone who can no longer play.
What makes losing Pronger even worse is the recent injury to Claude Giroux.
After being hit in the head by Wayne Simmonds' knee during Saturday night's game against the Tampa Bay Lightning, Giroux has not practiced and will miss Tuesday's game against the Washington Capitals, according to Sarah Baicker of CSN Philly.
What this means is that the Flyers are without their two best players. Giroux is the NHL's points leader who plays effectively in all aspects of the game. Pronger's value to the team is in the same tier of importance.
The Flyers have an excellent team with plenty of depth, but they have to be worried about losing their best two players to injuries.