A head injury has once again sidelined hockey's best player. The Pittsburgh Penguins announced that captain Sidney Crosby has been diagnosed with a concussion, and there is no timetable for his return. What does this mean for the Penguins in the long and short term? And how should Pittsburgh adjust to his absence? Scott Burnside and Joe McDonald weigh in.

SCOTT BURNSIDE: The two words any hockey fan -- and especially any Penguins fan -- never wants to hear together are "Crosby" and "concussion." But they were uttered once again on Monday, and it’s hard not to get a bad feeling about it.

I was on hand on that rainy New Year's Day in 2011 when David Steckel clipped Crosby late in the second period of the Winter Classic at Heinz Field. A few days later, Crosby was slammed into the boards by Tampa Bay’s Victor Hedman. Crosby did not play again until the following November. He would also miss significant time after a recurrence of post-concussion symptoms later in the 2011-12 season and finish with just 22 games played.

Now we get word that Crosby suffered a concussion in practice on Friday and is out of the Penguins lineup, with no timeline for his return.

I’ll be heading to Pittsburgh for the Pens’ season opener on Thursday but can’t imagine there’ll be much joy as their 2016 Stanley Cup banner is raised to the rafters of the newly renamed PPG Paints Arena if Crosby isn’t sporting a pair of skates and his trademark No. 87 along with his teammates. Joe, you spent some time with Crosby this summer during his time with the Stanley Cup in Nova Scotia, and it seemed he really appreciated the experience given the uncertainty that had plagued him during his recovery from those earlier concussions.

JOE McDONALD: You’re right, Scotty. He was extremely appreciative of his second Stanley Cup title for that exact reason. During the week I spent with Crosby in July in Cole Harbour, he discussed how he felt during those two seasons while dealing with the concussions. While rehabbing in 2011-12, he wasn’t focused on winning another Stanley Cup. It was all about his health first and foremost.

“When you’re going through a concussion, you’re more thinking about, ‘Am I going to play?’ And the Stanley Cup is the last thing on your mind," Crosby said in July while recalling what it was like for him a few seasons ago. "It was more or less just when and how I was going to feel when I did get back."

Now he’s dealing with another concussion. Having spent plenty of time researching the effects of head injuries and speaking with some of the best doctors in the world about concussions, I've learned that there’s no magic number as far as how many are too many. It could be only one, or it could be several concussions, depending on the individual. If we’ve learned anything, it's that any concussion should be taken seriously. There’s no timetable on his return at this point, but let’s hope Crosby is 100 percent healthy when he does return.

BURNSIDE:The game is always poorer when its best players aren’t able to play because of injury. Is there any doubt that Crosby has played the best hockey of his career over the past seven or eight months? After having a five-point October, he lit it up under new Penguins coach Mike Sullivan and was full value for his Conn Smythe Trophy win as playoff MVP. Then he followed that with a dominant performance at the recent World Cup of Hockey, where he led all players in points.

In short, he has reinforced that he is the best player on the planet. All of which makes this diagnosis so difficult to accept. On the ice, history tells us it’s almost impossible to repeat as Cup champs, but we figured that with Crosby playing the way he has been playing, the Pens would have as good a shot at doubling down next June as any team in recent history. Without Crosby? Nope. Not a chance. The Penguins are deep up front, but if Crosby is out for any length of time it’s going to put a lot of pressure on Evgeni Malkin to step up. Malkin is coming off a pretty ordinary World Cup, so he’ll have to find another gear if the Penguins’ captain is gone long term.

McDONALD: No one, and I mean no one, can replace Sidney Crosby. He has again demonstrated his ability to make everyone around him better, and that was on display during the Stanley Cup playoffs en route to a championship and again as he led Team Canada to the World Cup of Hockey victory. He’s only 29 and should be in the prime of his career. His linemates for Team Canada, Patrice Bergeron and Brad Marchand, marveled at how Crosby can dominate a game in the simplest ways.

You’re right, Scotty, that the Penguins are deep, but Malkin has shown me very little in the last calendar year to prove he can take over the reins in Crosby’s absence. Phil Kessel, who played well during the playoffs and was a close second to Crosby in the Conn Smythe voting, is more effective as a third-line player in Pittsburgh’s system. Again, hopefully this is not a long-term issue for Crosby or the Penguins. If you were coach Mike Sullivan, Scotty, how would you handle it?

BURNSIDE: Well, ageless wonder Matt Cullen skated in Crosby’s place with Conor Sheary and Patric Hornqvist, and in the short term that’s not a bad fit given Cullen’s skill set. Cullen is coming off a strong playoff, but he is going to turn 40 in less than a month. And the Penguins are deep down the middle, with Nick Bonino and Malkin giving opposing coaches fits when they try to come up with a game plan to keep the Penguins in check.

As I was putting together the Metropolitan Division previews, I had Washington and Pittsburgh as the only two locks in the eight-team division, definitely a cut above the rest of the division. But if Crosby is out long term that’s going to make things even murkier. You mentioned Sullivan. I still think it’s a shame he wasn’t recognized with a spot on the Jack Adams Trophy final ballot, given his work in unleashing the Penguins’ potent offense. But coaching without Crosby will provide a stern test for Sullivan given how important Crosby is in setting the tone on and off the ice for the defending Stanley Cup champs.

McDONALD: I couldn’t agree more, Scotty, as far as Sullivan for the Jack Adams last season. I’m willing to bet that Sullivan has talked to his players at some point since Crosby’s diagnosis and that the coach explained the team will deal with this injury just like any other. This is an opportunity for other players to step up. You know how I feel about Malkin, and I do believe Kessel is best at his current role, but maybe this is the time for Phil to stake his claim once again as a potent offensive force. His line, with Carl Hagelin and Bonino at center, should be crucial for the Penguins during Crosby’s absence.

I do like your idea about Cullen, but I’m not sure he’ll be able to play the type of minutes required of him in that top role, especially given his short summer. It’ll be interesting, no doubt, to see how the Penguins deal with this situation, but here’s hoping the best player in the world will return healthy and productive once again, because if there’s a team I want to see repeat as Stanley Cup champions, it is this version of the Pittsburgh Penguins, led by No. 87.