A lot of attention gets paid to the power play in NHL hockey. Even though most of the game is played at five-on-five, dissecting the power play takes up a lot of the oxygen in commentary. Chris Krieder led the NHL this year with 25 power play goals, so it certainly seems important just from that point of view.
If you cast your mind back to last October, you might remember we focussed a little on the crackdown on cross-checking in the NHL. The refs called a lot more penalties for a while, and then, as we watched the power-play opportunities number decline week by week, they stopped.