The St. Louis Blues have quite the history with the Boston Bruins. There was never much of a rivalry prior to the 2019 Stanley Cup Final.
In fact, the Blues had lost 57% of all games against the Bruins. However, it can never again be said that the Blues did not win the biggest one against Boston. Now, the two are even on Stanley Cups won against the other.
But, the Bruins regained the regular season edge with a rather dominant 3-0 win back in October. You could tell they just wanted it more in that game, to get a small slice of revenge for that loss in Game 7 of the Stanley Cup Final.