Division Series
Quarterfinals of the MLB postseason
The Division Series (DS) is the quarterfinal round of postseason play in Major League Baseball, featuring the American League Division Series (ALDS) and the National League Division Series (NLDS). Under the current format, the top-two division winners in each league play best-of-five series against the two winners of the Wild Card Series from each league. The winners of the Division Series then advance to the League Championship Series for their respective league.
History
1981 season
The first use of the term "Division Series" dates to 1981, when, due to a mid-season players' strike, the season was divided into two halves. To attempt to balance the two halves of the season, the postseason was temporarily expanded to include a Division Series, with the winners of the first and second half from each division (East and West at the time) playing one another in a best-of-five series to decide which team would represent that division in the League Championship Series (this format being common in Minor League Baseball).
The temporary format did not come without flaws, however. One flaw was that, because the two halves of the season were independent of one another, the winner of the first half had no real incentive to try to win the second half as well. Even if one team finished first in their division in both halves, they would not receive a bye for the round, and would instead have to play the Division Series against the team that finished in second place for the second half.
In addition, a team that finished with the best overall record in the division over the course of both halves of the season could still miss the playoffs if they failed to place first in their division at the end of either half of the season. This was the case for the Cincinnati Reds, who posted a 66–42 overall record, the best over both halves in the National League West division, yet they missed the playoffs because they were in second place at the end of both the first and second half.
Begin with the source’s own compact description: “Division Series” is quarterfinals of the MLB postseason. The dossier treats that line as a proposition to test through Division, Series and Quarterfinals, not as a finished interpretation.
Why this record matters
The phrase “quarterfinals of the MLB postseason” supplies a clear boundary for inquiry. It also exposes the unanswered questions: who defined that boundary, when it became stable and which sources sit outside it.
Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Sep 25, 2026. The linked authority identifier is Q1049755. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank. The first chronological checks are 1981.
The absence of detail may reflect summary conventions rather than a lack of surviving documentation. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
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This entry incorporates text from “Division Series” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.