Rivalries add spice to any competition. If there is a history between two players or two teams, the competition becomes more intense. The stakes are higher, because it is no longer just a game, there is also pride at stake.

But when does a match-up develop into a rivalry? We cannot just call any tight game a rivalry, there must be some factors to qualify. The default component of a rivalry is multiple incidents of crucial matches. The Lakers-Celtics rivalry is the best example of this. There were classic series between the two franchises in the 60s, 70s, 80s and the 2000s. Since they would only meet in a series when they are in the Finals, then those are definitely crucial games.