Rivalries are formed as the result of many factors: political, geographical, and historical and in Major League Soccer's case often marketing.
Rivalries are consummated by meaningful games, those that are big not just because the two teams are playing each other, but in their importance in the standings.
The 401 derby, consisting of the Montreal Impact and Toronto FC has all of those aforementioned factors. Not only are the two team's rivals, despite both being less than 10 years old, the cities that they reside in have been at odds for centuries.
However there has always been something lacking about the 401 derby, especially in MLS play: the games have rarely had any greater significance.
When Montreal entered the league in 2012 they missed the playoffs, while TFC had their worst season in club history. When the Impact made the playoffs in 2013 Toronto had a poor year once again. Last year while Toronto came close to make the playoffs, the Impact had their worst year in club history.
For the first time this year both Toronto FC and the Montreal Impact are on track to make the playoffs, sitting fourth and sixth in the Eastern Conference respectively. Winning this game wouldn't just mean beating a rival, it would mean crucial points that could make or break a playoff appearance.
Three points could potentially put Toronto just one point out of third place, and only 11 points away from a first ever playoff appearance. It would also mean Toronto winning the season series between the two teams after Montreal beat them in the Voyageurs Cup semi-finals.
The game is even more important for Montreal, however, as the Impact are in a three team tie for the sixth and final playoff spot with expansion sides New York City FC and Orlando City SC. They will come in extra hungry after losing the Voyageur's Cup final to Vancouver yesterday.
More importantly it could be the first installment in a trilogy that would take this rivalry to new heights. Toronto and Montreal are scheduled to play on the final day of the season in a match that could decide several playoff fates.
One of such possibility, and the potential tip of the iceberg would be a playoff game between the two clubs. With their current positioning in the standings that is a real possibility, which would be guaranteed by the teams finishing third and sixth or fourth and fifth.
All of this is getting ahead of the present, as there are still 10 league games left and a small chance that the Impact, or an even smaller chance that Toronto, could drop out of the playoffs altogether. But it shows what this game could be setting the stage for down the road.
That stage will also be filled with a more interesting cast than ever before for both sides. Saturday will be the first time that Didier Drogba plays in Toronto, and he will join a strong cast with Laurent Ciman, Michael Bradley, Sebastian Giovinco and Jozy Altidore.
Even without Ignacio Piatti, who will miss the game due to a calf injury, this is undoubtedly the best game between these two sides in terms of player quality.
Coincidentally, it is also the most important 401 derby since the rivalry debuted. That in itself should make it the highlight of what promises to be a thrilling MLS rivalry week.
The Montreal Impact are undoubtedly one of Toronto's biggest rivals, but Saturday's game could kickstart the process to insuring that they become the club's biggest rival, bar none.