The most difficult thing about being a hockey fan is truly understanding what's happening on the ice. Sure, a lot of people think they know what's going on, and that includes me sometimes, but the truth is that sometimes truly understanding why things are happening requires NHL experience and a time consuming break down of post-game video. For that reason I'm not going to try to analyze why the Bruins are facing elimination against the Hawks. But I can make some observations based on what we've seen so far.
All season long the Bruins have had a "Jekyll and Hyde" personality, sometimes playing a strong defensive game that frustrates opponents, combined with a quick break out, razor sharp passing, and a deadly ability to cash in on mistakes.
At other times they have played like little old ladies. They turn the puck over in their zone, the forwards fail to get back quickly to back check, and their rushes come to nothing. This gets us back to why this happens. If your team plays badly, is it because they didn't show up to play or is it because the other team is taking away time and space? I don't think I'm going out on a limb to say that during the regular season much of the poor play of the Bruins was not the result of pressure from the opposing teams. The Bruins simply didn't play at their best. Whether or not the Bruins brought their best in game 5 is up for debate. My feeling is that they did not, but like I said, I can't be sure.
On a related note, for whatever reason the Bruins have not been able to shutdown the Hawks with their layered defense in the same way they did the Penguins. Whether that is due to the speed of the Hawks, the players not "playing their game," or as an intentional strategy of Julien's, I'm not going to pretend to know. It is entirely possible that we will see the Bruins shut the Hawks down in game 6. If so, then the Bruins have a very good chance of winning the series. Otherwise the Bruins will have to beat the Hawks at their own game, and while I believe they can, a Bruins Cup win is somewhat less assured.
I do know that the Bruins can play with much more desperation! Bruins fans can hope that game 5 was a momentary lapse of focus and determination in a long post season and the Bruins will be back in game 6, with or without Bergeron.