Qualifying
Each league contains three divisions, and each division winner qualifies. The remaining places go to the best records among everyone else, regardless of division, which stops a strong team being punished for sharing a division with an even stronger one.
The top seeds skip the opening round, which in a sport this dependent on pitching rotation order is a genuine structural advantage: it lets a team line up its two best starters for the first series that matters.
Everyone else begins with a very short series, sometimes decided in two games. After one hundred and sixty-two matches, a season can end in forty-eight hours — a compression that generates most of the sport's annual arguments about fairness.
Why the best team so rarely wins
Baseball's regular season is long enough to be genuinely informative. Over that many games, the better team wins clearly more often, and the standings by September are an honest ranking. The postseason then discards nearly all of that evidence.
The reason is that baseball's game-to-game randomness is unusually high. Even a dominant team loses around a third of its games, so a five- or seven-game series between two good teams is close to a coin flip weighted slightly toward the better side. Repeat that three times and the strongest team's chance of surviving is modest.
This is not a flaw the sport is unaware of. It is the accepted price of a postseason, and it is why baseball's champions are described as the team that got hot rather than the team that was best — an honesty other sports could learn from.
October baseball is a different game
With no need to preserve arms for next week, managers use their best pitchers far more aggressively. Starters work on short rest, relievers appear in consecutive games, and a pitcher who threw two innings in April might throw two innings in three straight days in October.
Lineups shorten too. Platoon advantages are pursued relentlessly, defensive substitutions arrive earlier, and the bench is used with a freedom that would be reckless across a long season.
The result is a version of the sport with less depth and more intensity, where a single defensive misjudgement is replayed for a decade. It is also why regular-season records are a poor guide to what happens once the bracket starts.