MLB Tiebreaking Procedure

1. The text above says nothing about five-or-more-team ties (MLB's own document stops at four -- presumably because a division has at most 5 teams and a genuine 5-way tie surviving every one of these criteria is considered outside the realm of realistic possibility). PlayoffRace extrapolates the visible pattern for that case (a club that beats every other tied club individually qualifies outright; otherwise rank by winning percentage among the tied clubs combined, narrowing via the same intradivision/intraleague/half/half+1 criteria) rather than leaving it unhandled — marked throughout as an extrapolation beyond the sourced text, not something MLB has itself published.

2. ONE SPOT PER APPLICATION of the procedure. Every branch of the text ends by naming the club that "qualifies" -- one club, for one spot ("If four teams are all tied for one spot, the winner would be determined via..."; "The Club with the highest overall winning percentage in that group qualifies"; "the two-Club tiebreak rules ... to determine the qualifier"). Once that club is identified, the clubs left over are a fresh, smaller tie for the NEXT spot and revert to the procedure for their new size, recomputed over just those clubs (the three-club Note says exactly this for the remaining two; the same rules "also apply to situations in which ... three teams tie for three spots and the exact seeding for those teams must be resolved"). So a four-club tie is a four-club procedure for the first spot, then a three-club procedure for the second, then a two-club one for the third -- and a ranking step (combined record, or any cascade step) places ONLY its leader; when two or more clubs share the top figure, the procedure for that many clubs picks the qualifier from among them and the loser(s) go back into the pool. This can order the later spots differently than one reading of the whole ranking would; a four-club cycle where it does is among PlayoffRace's checked cases. The principle: every seed a club has qualified for is explained in full, each progression and each reversion. It is also the reading under which independent external comparisons agree with PlayoffRace's clinch numbers.

3. No coin toss or equivalent formula closes out a tie unresolved even after the full expanding-window step -- MLB's own materials describe this as "commissioner's discretion." Given how granular that step is, this is expected to be essentially theoretical.

4. "Head-to-head record" and "winning percentage in games among the tied Clubs" are the same underlying computation (a club's combined record against the other tied clubs) at different pool sizes -- implemented once and reused, per the text's own two-team and four-team wording lining up exactly this way.

5. "Last Half of Intraleague Games Plus One" (two-club step 5, and its three/four-club "last half plus one" counterparts) is read as a CUMULATIVE percentage: each club's own second-half intraleague games plus that club's last first-half intraleague game, compared as one record; if still tied, the previous first-half game is added too, one game at a time. It is NOT a comparison of the single added game's outcome (win vs. loss). The window is matched per club by game count, not by calendar date, since clubs don't all play the same number of intraleague games before the break -- so a club with 40 second-half intraleague games is scored over 41 at the "plus one" pass while a club with 38 is scored over 39, and so on. If a club walks back through its entire first half before the tie breaks, it is simply scored on its full intraleague record from then on while the other clubs' windows keep growing (impractical in a real season, but that is the reading).

This addendum is PlayoffRace's own. It is NOT part of MLB's published text and must never be merged into it -- the procedure above stays byte-for-byte. It states explicitly the rules that text fixes only by structure, cross-reference or analogy, so that neither a reader nor a future implementation can arrive at a different answer without noticing they have. Each rule names the source language it rests on and, where a competing reading exists, names that reading and says why it is rejected. The sourced text governs: if a rule here is ever shown to contradict it, the rule is wrong and this addendum should be corrected -- it is not a licence to diverge.

A1. A RANKING STEP PLACES ONLY ITS LEADER.

Rule.Every step that produces an ordering -- "ranked by their overall winning percentage amongst the other Clubs combined" (three Clubs), "highest winning percentage in games among the tied Clubs" (four Clubs), and every cascade step at any pool size -- awards ONE spot, to the Club at the top. What that ordering said below first place has no effect on anything. The Clubs not placed return to the pool for the next spot, and the procedure begins again at its first step, over only those Clubs, at the size they now number.

Source.Every branch of the sourced text ends in the singular: "then Club 1 qualifies"; "The Club with the highest overall winning percentage in that group qualifies"; "the two-Club tiebreak rules ... to determine the qualifier"; "If four teams are all tied for one spot, the winner would be determined via ...". The Note states the reversion outright for three Clubs: "once the above is used to determine the division champ, the remaining two teams revert to the two-team tiebreaker procedure to determine the Wild Card."

Competing reading, rejected.That the three-Club ranking is a three-Club ordering -- first spot to first place, second spot to second place. Rejected because the sentence producing the ranking places only the Club "with the highest overall winning percentage," and because the Note sends the leftovers back to a procedure whose FIRST step (head-to-head) is not the ranking that just ordered them. The two readings disagree on real seasons. Worked example, verified against PlayoffRace's engine: A beats B 5-1, C beats A 4-2, B beats C 4-2. No Club has a better record against each of the others. Combined records among the tied Clubs: A 7-5 (.583), C 6-6 (.500), B 5-7 (.417) -- the ranking reads A, C, B. A qualifies for the first spot. B and C revert to the two-Club procedure, where B won the season series 4-2 and takes the second spot. C, second in the ranking, is the Club eliminated.

A2. WHAT "REVERT" MEANS.

Rule.The Clubs left over form a fresh tie of their new size, and every figure is recomputed over only those Clubs, from the first step of the procedure for that size. Nothing carries forward: not the ranking, not which steps were already spent, not the numbers computed at the larger size. A Club's head-to-head record against a pool of three is not its head-to-head record against the two that remain, and the earlier value is never reused.

Source.The Note's "revert to the two-team tiebreaker procedure"; the four-Club footnote sending sub-pools to "the two-Club tiebreak rules" and "the three-Club tiebreak rules"; and the generalization clause, under which the same rules "also apply to situations in which ... three teams tie for three spots and the exact seeding for those teams must be resolved" -- repeated application, not one pass.

A3. CLUBS SHARING A STEP'S TOP FIGURE.

Rule.When two or more Clubs share the top figure at any step, the procedure for that many Clubs runs over just them and identifies the qualifier. The Clubs that lose it take nothing by having shared the lead: they go back into the pool with everyone else, and the next spot starts again at step one per A1 and A2.

Source."If two of the Clubs have identical winning percentages, then they would follow the two-Club tiebreak rules to break their tie to determine the qualifier" -- the qualifier, singular, with nothing said about where the loser lands. The four-Club footnote is worded the same way.

A4. THREE CLUBS TIED FOR TWO SPOTS.

Rule.Run the three-Club procedure for the first spot. The two Clubs remaining revert to the two-Club procedure for the second. The Club that loses that is eliminated. There is no third application. This holds whatever the two spots are -- a division championship plus a Wild Card, two Wild Cards, or two seeds among Clubs already assured of a berth.

Source.The Note states exactly this for a division championship plus one Wild Card, which is itself a three-for-two case. The generalization clause lists "two teams tie for two spots" and "three teams tie for three spots" and omits three-for-two; the omission is read as incompleteness of the list rather than exclusion of the case, because the sourced text supplies no mechanism that varies with what kind of spot is at stake, and A1 is not conditional on one.

Note.Where both spots are postseason berths, their order still matters: the first-spot qualifier is the higher seed.

A5. THE "PLUS ONE" PROVISO IS EVALUATED AGAINST THE CURRENT POOL.

Rule.In "provided that such additional game was not between any of the tied Clubs," the tied Clubs are the Clubs tied in the application being run. A game against a Club that was placed or eliminated at an earlier spot is not excluded at a later one. And because the two-Club procedure's step 5 carries no such proviso at all, at a two-Club pool no game is excluded from the expanding window -- including a game between the two tied Clubs.

Source.The proviso appears only in the three-Club and four-Club "last half plus one" steps; the two-Club step 5 omits it. That asymmetry is in the sourced text, not in this reading of it, and the text is followed as written at each size rather than harmonized across sizes.

Consequence.Stated here so it is not later mistaken for a defect: the same game between Clubs B and C can be excluded while the first spot is decided and counted while the second is.

A6. "A BETTER RECORD AGAINST CLUBS 2 AND 3" MEANS AGAINST EACH SEPARATELY.

Rule.The check passes only for a Club holding a winning season series against every other Club in the pool individually. At most one Club can ever satisfy it. A Club with the best combined record against the others, but a losing series against one of them, does not satisfy it and does not qualify at this step.

Source.The four-Club procedure writes the same check explicitly as "Tied Club with better record against each of the three other Clubs."

Competing reading, rejected.A better combined record against the pair -- which would make this check identical to the ranking in the branch immediately below it and leave that branch nothing to decide.

A7. "IDENTICAL RECORDS AGAINST ONE ANOTHER."

Rule.Read as every pairwise season series within the pool being exactly even.

Note.The alternative reading -- every Club's combined record against the others being equal -- selects a different branch but reaches the same cascade, so no outcome depends on the choice. A pool in which every series is even also has every combined record equal. A pool with equal combined records but uneven series (a cycle) has no dominant Club, since a Club winning every series would have a strictly better combined record than at least one other; the ranking therefore finds every Club identical and ends by directing the reader back to "the tiebreak rules above (No. 1) for three clubs having identical records against one another." Both roads end at the same cascade. The two readings differ only in which steps a trace displays.

A8. SCOPE.

These rules add nothing to the sourced procedure's criteria and change none of them. They fix the order and repetition in which the sourced criteria are applied. Matters already covered in the notes above -- ties of five or more Clubs, the cumulative reading of "last half plus one," the per-Club matching of the expanding window by game count, and the absence of any final tiebreaker below commissioner's discretion -- are not restated here.