Here's some numbers I pulled up re: Boston 2013-14 vs 2014-15:
As many know, Bergeron is their best forward, and has been for a while. His impact on the possession of the Bruins in the last two years is
huge (and about the same both times at +9.2%)
The major difference is, last year when Bergeron was off the ice, the Bruins controlled 53% of play, which is pretty damn good, and would be 6th in the league. (In reality they were 3rd, because Bergeron is awesome).
This year, when Bergeron's off the ice they only control 49.5% of play, which is good for 19th in the league. Massive drop-off. They are basically bad unless Bergeron is playing, and that's a big problem; he can only do so much.