These two teams simply don't like each other, as they exhibited in a first period scrum that spilled into Pittsburgh's bench.
The incident started when Capitals forward Tom Wilson sent Penguins forward Chris Kunitz into the boards. Pittsburgh's Blake Comeau came to his teammates defence and chaos ensued.
The scrum saw Tom Wilson, Michael Latta, Blake Comeau and Steve Downie receive minor penalties.
It was only a week ago that these teams met for another chippy edition of their long-time rivalry.
Wilson wasn't on his best behaviour even before the puck dropped. The 20-year-old may have drawn some attention with a small shove to Penguins star forward Evgeni Malkin prior to the game.