Teams that over-rely on the power play for goal differential struggle in the playoffs as the frequency and variability of penalties called increases. Penalty calls are influenced by score and game-state, and infractions that occur later in games, later in series, and later in the playoffs are called less often, giving these teams less opportunity to leverage the power-play for goal differential.
Additionally, the average quality of goaltending and penalty killing faced generally increases in the playoffs vs the 82 game schedule, making it more difficult to score power-play goals when power-plays are awarded.
The bulk of the games are played 5v5, and the most successful teams are overwhelmingly the teams that control play and generate goal differential at 5v5. Sometimes you get a team like Edmonton, that is underwater in 5v5 goal differential, but these are teams that control play with poor sh% or sv% or both.
