It turns out the Bruins were fairly hurt during their series with Carolina. We already knew Andrew Ference had a serious issue, and it turns out that it was a torn groin. Phil Kessel had a torn rotator cuff and labrum. David Krejci had a problem with his hip. And Chuck Kobasew broke two of his ribs in Game 1.
Krejci, Kessel, and Ference will all require surgery. Kessel and Krejci will miss 4 to 6 months, which means missing at least the start of the 2009-2010 season.
This isn't an excuse for losing to Carolina, but it's a partial explanation. Those are three lines which lose their ferocity with injured players.
The silver lining to this is that Kessel and Krejci are both restricted free agents. Other teams may be more reluctant to give them big offer sheets (and potentially forfeit draft picks) when these guys are fresh of a surgeon's table.