Derek Lalonde could make changes to the defensive system

The famous “man-to-man” defensive system has been heavily criticized because, clearly, it didn't seem to be working.
In fact, it's not a bad idea, but this might not be the best team to execute it effectively. Furthermore, it might not be used as effectively as it should be.
It's fine to shadow a player, but only to a certain extent—especially in today's hockey. Talented players, especially forwards, like to roam all over the ice, even more so during a power play.
However, the