The Stanley Cup playoffs ask sixteen teams to win sixteen games across four best-of-seven rounds, in a sport where a goaltender having a good month can beat anybody.
Qualifying
Each conference sends eight teams. The route in is divisional rather than purely by record.
The top three teams in each division qualify automatically, which is six teams per conference. The remaining two places in each conference go to the wild cards: the two clubs with the best records among everyone who did not finish in a division's top three, regardless of which division they come from.
This means a conference can send five teams from one division and three from the other, if one division is much stronger.
The bracket
The first round is played inside the divisions. Each division's second and third-placed teams play each other. Each division winner plays a wild card, with the conference's stronger division winner facing the weaker wild card.
Winners meet in the divisional final, and those winners meet in the conference final. The two conference champions contest the Stanley Cup Final.
The bracket is fixed rather than reseeded, so beating a strong team in round one does not earn you an easier round two.
Best-of-seven, and the overtime that changes everything
Every round is best-of-seven in a 2-2-1-1-1 pattern, with home ice going to the higher-seeded team.
Playoff overtime is the defining feature. There is no shootout. Teams play full twenty-minute periods at even strength until somebody scores, with intermissions in between. Games have run to three, four and even more overtime periods. One shot ends it, whenever it comes, however long it takes.
Why upsets are common
Three reasons. Goaltending is the most volatile position in team sport, and a hot goalie can steal a series on his own. Scoring is low, so a single deflection swings a game in a way a single basket never does. And the physical cost accumulates: a team that grinds through a seven-game first round arrives at round two visibly diminished.
The result is a postseason where the team with the best regular-season record frequently does not lift the trophy, and where the eventual champion often survives at least one series it looked like losing.
Points, not wins
One thing that confuses newcomers: qualification is decided by points, not win percentage. A win is two points, an overtime or shootout loss is one, a regulation loss is none. A team can miss the playoffs despite more wins than a rival, because the rival collected more single points in defeat.
The short version
Three per division plus two wild cards per conference. Divisional first round, fixed bracket, four best-of-seven rounds, and overtime that keeps going until a goal decides it.