In baseball, the Division Series is the official name for the quarterfinal round of the Major League Baseball playoffs with the addition of a sudden death Wild Card Game. Currently, a total of four series are played in this opening round, two each for both the American League and the National League.
1981 season 
The first use of the term "Division Series" dates from 1981, when due to a mid-season players' strike, that season was divided into two halves, with the winners of each half from each division 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). But 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 (since, unlike in the minor leagues, if the same team did win both halves it was not given a bye into the next round), and a team that won neither half could have actually had the best overall record in the division; indeed, the latter actually occurred, as the Cincinnati Reds not only had the best won-lost record (in both halves of the season combined) among the six teams in the National League's Western Division (to which they belonged at the time), but the Reds had the best overall winning percentage in all of Major League Baseball, yet did not advance to the playoffs because they did not finish first in either of the two halves. Until 2012 this was the only Division Series which actually consisted of teams from the same division playing each other.
1993–1994: Proposal, Realignment, and Cancellation of 1994 Postseason 
In 1993, the owners approved to bring back the Division Series, given the fact that three of the four series went to a Game 5. Originally the format called for the top team in the AL East to play the 2nd place team on the AL West and vice-versa. In 1994, both the National League and the American League realigned, with the number of divisions in both increasing from two to three (with fewer teams in each). At the same time, the number of teams qualifying for baseball's postseason was doubled, from four to eight; henceforth the three first-place teams from each league's divisions would reach the postseason, along with one wild card team from each league (the latter being the second-place finisher with the best regular-season record). However, this expanded playoff format would not return until the following year, because a players' strike, which began on August 12, 1994, led to the cancellation of that season's playoffs and World Series (and caused the 1995 regular season to have 18 fewer games for each team than normal).
1995–1997: Pre-arranged Seeding 
Throughout its existence, the Division Series has been best-of-five; however, both the method of awarding home-field advantage in the series and which games the team getting the advantage would host were changed in 1998.
Originally, the Eastern, Central and Western Division champions rotated home-site priority, with the two of them getting the extra home game and the third one and the wild card not. The 2–3 format was used in which the team with the disadvantage hosted the first two games and the team with the advantage hosting the remaining game(s). This meant the team with the disadvantage had absolutely no chance of winning the series at home. A similar format had also been used for the League Championship Series from 1969-1984. It also allowed the disadvantaged teams the unusual luxury of starting a series at home, possibly having home field advantage in a three game series, and a guarantee that they play the maximum number of games possible at home (2).
This format was changed in 1998 because there was a 39.5% chance each year that at least one of the leagues would have their top two division champions meet in the Division Series, allowing the worst division champion to have the "advantage" of playing the wild card.
The two division champions with the best regular-season records have been accorded with the home field advantage. Also, the format changed to a 2-2-1 layout with the team having home-field advantage hosting the first, second and (if necessary) fifth games; with this newer format, the lower seeded team actually gets two chances out of three to win the series on its home field although the higher seeded team hosts three out of five games overall. In both the AL and the NL the three division champions are automatically given the top three seeds, seeded 1-3 based on record, and the wildcard is given the 4th seed regardless of record. In both the AL and the NL, the 1 seed played the 4 seed and the 2 seed played the 3 seed, unless the 1 and 4 seed are in the same division. Because teams from the same division cannot play each other in the first round, if the normal matchups would cause this, then the 1 seed played the 3 seed, and the 2 seed played the 4 seed. In all cases the 1 and 2 seed have home field advantage. From 2007–2011, the 1 seed of the league that wins the All-Star game is given another advantage, being allowed to choose their schedule for the series. They can either choose to have an extra day off (usually between games 1 and 2) during the division series and start a day early, or start a day late, with one less off day (only having travel days off, between games 2 and 3, and if necessary 4 and 5). The American League's best record received this option from 2007–2009 and the National League's best record received it in 2010. It was discontinued in 2011.
A revised playoff system was utilized beginning with the 2012 season, which added a second wild card team for each league. The two wild card teams in each league play a one game playoff to advance. The winner of this game automatically faces the number 1 seed in the league in the Division Series, regardless of whether or not they are in the same division. Due to scheduling conflicts, the 2012 Division Series featured the lower seed hosting the first two games, with the higher seed hosting the next three games. For 2013 and beyond, the Division Series will return to the 2-2-1 format previously used. The format calls for the wild-card series to begin on the second day of the Division Series. So if the Division Series start on October 2, then the Wild Card team will play on October 3.
Criticism of scheduling 
There has been some criticism on how Major League Baseball schedules Division Series games. Teams with large national fan followings like the New York Yankees are almost always scheduled to play in prime time at 8 p.m. ET/5 p.m. PT to generate the highest TV ratings. As a result, West Coast teams generally have to play on the road at 1 p.m. ET/10 a.m. PT when many of their fans are unable to watch the game because they are at work or school. Conversely, when games on the West Coast are played at 10 p.m. ET/7 p.m. PT, many fans on the East Coast are unable to watch a game in its entirety, due to games ending around 1 a.m. ET/10 p.m. PT, while most West Coast fans are able to watch the entire game.
However, during the inaugural and 1995 seasons, the Division and League Championship Series was aired by the league's television operation, The Baseball Network, a syndication package between ABC and NBC. In order to increase viewership, all games were played in primetime at consistent times, and each affiliate of the network carrying the series could only air one of the games each night, determined by the station's area. While this prevented the issue of afternoon games (and did, as planned, increase viewership), the plan drew ire from critics for not allowing viewers to choose the games they want to watch during the post-season.
See also 
- MLB division winners
- American League Division Series
- National League Division Series
- MLB postseason
- List of Major League Baseball franchise postseason streaks
- List of Major League Baseball franchise postseason droughts
- List of National League pennant winners
- List of American League pennant winners
- League Championship Series
- American League Championship Series (ALCS)
- National League Championship Series (NLCS)
- World Series
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- 2012 MLB Postseason Schedule MLB.com
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