Any sports fan can tell you that injuries are a part of the game. But not all injuries are created equal.
Sometimes, injuries make very little difference, as players are not out of action for long or are replaced by another player who is able to step up and play as well as—or better than—the player who was hurt.
But sometimes, injuries change the course of a team's season. Some players cannot be adequately replaced, and the absence changes the course of the team's year.
Here is a look at some of the most important injuries in the NHL this season.
Chris Pronger's importance to the Philadelphia Flyers cannot be underestimated. He is the Flyers' best defenseman and their captain and on-ice leader.
Pronger can really do it all for the Flyers. He provides scoring from the blue line, contributes to both the power play and penalty kill and is also a very strong presence in his own zone.
Most importantly, Pronger is a minutes muncher. When he plays 25 or more minutes a game, the other defensemen on the Philadelphia roster are less taxed and have more defined roles. Pronger's presence on the ice makes the players around him better.
Unfortunately, the concussion that ended Pronger's season could also be career threatening. Pronger's absence has hurt Philadelphia during the regular season, but during the playoffs, where match-ups are key and overtimes tax the stamina of a team, Pronger's absence will be felt even more acutely.
It's impossible to exclude the man considered by many to be the best all-around player in hockey from a list of key injuries.
Crosby is set to return later this week, but thus far, he has played only a handful of games this year after missing the entire second half of last season.
Evgeni Malkin has picked up the slack offensively and the Penguins have remained competitive in the Eastern Conference, but adding Crosby for the playoffs takes a team that was very good and turns them into instant Stanley Cup contenders.
Crosby will have about 15 games to play himself into shape and get ready for the playoffs.
If Crosby, Malkin and Jordan Staal are all healthy, the Penguins are as talented at center as any team in the NHL.
Brenden Morrow is back in the lineup for the Dallas Stars, and for the Stars organization, his return couldn't come soon enough.
Morrow is the captain in Dallas for a good reason. He's a veteran who leads a young Stars team that is just learning to win again after rebuilding the past two seasons.
Last year, Morrow scored 33 goals while appearing in all 82 games. This year, he has only nine goals in just 44 games.
Dallas got off to a fast start with Morrow in the lineup, slumped when he was hurt and has started to compete again for a playoff berth in the Western Conference since his return to action.
As long as Morrow remains healthy, the Stars have a chance.
Martin Havlat was acquired by the San Jose Sharks from the Minnesota Wild this summer.
The Sharks acquired Havlat to replace the offensive production they lost when dealing forwards Dany Heatley and Devin Setoguchi to Minnesota in separate deals.
Havlat was just adjusting to life in San Jose when he suffered a hamstring injury in December, and he has not played since.
The 30-year-old Czech scored only two goals and 13 assists in 26 games for San Jose before the injury.
The Sharks have slumped badly down the stretch and are now in danger of missing the playoffs for the first time since 2003. Their biggest problem: a lack of offense.
Havlat is expected to return to the lineup in late March or early April. The only question is whether or not that will be in time to salvage the Sharks' season.
The Washington Capitals were one of the favorites to emerge from the Eastern Conference this year, but now they are in a fight just to reach the playoffs.
One reason for the Caps struggles is the loss of center Nicklas Backstrom for a good part of the season. Backstrom has been out of the lineup since the beginning of January.
Backstrom is the center on Washington's first line, and he has been the pivot for Alex Ovechkin for the past several years. Ovechkin has struggled all season, and the loss of Backstrom is one major reason for it.
Backstrom has appeared in only 38 games this season. He has scored 42 points, still better than a point-per-game clip, but without him, the Caps top line just doesn't have the same fire.
The Swedish center's presence is definitely missed in DC.
The Bruins lost backup goalie Tuukka Rask a few weeks ago, and the timing couldn't be worse for the defending Stanley Cup champions.
With Rask out for at least three weeks and possibly more, the Bruins signed veteran Marty Turco, who hadn't played in the NHL all season.
Just ask New York Rangers fans what the loss of a valuable goalie can do to a team during the playoff stretch drive. Last season, the Rangers lost Martin Biron in the final weeks of the season and Henrik Lundqvist had to play nearly every remaining game. Lundqvist was tired and not on top of his game when the Rangers reached the playoffs.
Since Rask's injury, Tim Thomas has appeared in eight straight games (starting seven of them). He will continue to play nearly every game until Turco is ready or Rask returns.
An injury to a backup goalie may not seem like a game changer, but having an overworked and tired goalie to start the marathon that is the Stanley Cup playoffs is not good for any team, especially one trying to repeat as Cup champions.