Five series-changing injuries

1. Sidney Crosby, Pittsburgh Penguins

Indeed an obvious place to start, but you wonder how No. 87 will stand up to the rigors of playoff hockey, where the hitting and physical play intensifies. So far, he's shown no negative signs since his second comeback. But his health will be a constant concern until the Penguins' season is over.

2. Daniel Sedin, Vancouver Canucks

The Canucks star suffered a concussion when elbowed in the head by Chicago's Duncan Keith last month and smartly was shut down by Vancouver for the rest of the regular season. Like Crosby, the question revolves more around how he's going to fare once he returns. How will he react when he gets his next big hit? The Canucks' Cup hopes lie with a healthy Daniel Sedin contributing in normal fashion.

3. Jonathan Toews, Chicago Blackhawks

Well, you see the pattern here. Just like Crosby and Sedin, Toews is the straw that stirs his team's drink. The Blackhawks were impressive in their captain's absence late in the regular season, but the truth is, without a healthy Toews, they can't expect to ever contend for the Cup. Again, we know Toews is coming back, but how will he be in these playoffs?

4. Chris Pronger, Philadelphia Flyers

Hats off to the Flyers, who have excelled this season despite a massive injury loss early in the year when captain and top blueliner Chris Pronger went down with a career-threatening concussion. The pre-deadline additions of Nicklas Grossmann and Pavel Kubina certainly help fill some of that void, but the reality is that this is the time of year when you remind yourself how much Pronger is missed. For my money, he's been the league's preeminent playoff warrior for the past decade; a fearless leader who raises his game at this time of year. He was integral when underdog Edmonton reached the 2006 Cup finals, when the Ducks won the 2007 Stanley Cup and when the Flyers reached the 2010 Stanley Cup finals. Playoff teams thrive with Pronger in the lineup. The Flyers will sorely miss him even more now that we're in playoff time.

5. Nathan Horton, Boston Bruins

He hasn't played since Jan. 22 due to a concussion -- his second major concussion in a year, after getting drilled in last June's Cup finals. While Horton may lack the profile of the four superstars mentioned here above him, his absence has been deeply felt by the Bruins. The Bruins' top-six forward group at times has simply felt off-kilter without him. The B's have generally done a good job of adjusting without him, but he's a bigger loss than most people around the league realize.