Defense wins championships. Every sports fan knows that saying because no matter what sport you indulge in, the saying fits the bill.
In other words, a team could have the strongest and most dominant offensive lineup of any team in a league, but without a competent defense, they will never get very far. So you could score five goals a game in the NHL, but that doesn’t get you very far when the defense gives up six (i.e. the 2014-15 Dallas Stars).
On the other hand, if a defense can hold the opposition to one or two goals a game, then the offense has a better shot at finding two or three goals and getting the win.