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 and 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. The concept of the "split season" was first used in 1892 to determine the NL pennant. Boston won the first half and Cleveland won the 2nd half, and they met in a League Championship Series won by Boston. (American Association had disbanded after 1891 season following 10-year run)
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 make its debut 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).
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. Before that year, the Eastern, Central and Western Division champions rotated home-site priority, with two of them getting the extra home game and the third one and the wild card not; since 1998 the two division champions with the best regular-season records have been accorded this privilege. Beginning in the same year, the team having home-field advantage has hosted the first, second and (if necessary) fifth games; before that the team with the disadvantage played the first two games at home and the team with the advantage the last three.
A wild card team can never receive home-field advantage in a series, even if it has a better record than the division champion it plays (which would occur if the teams with the two best records come from the same division; see below).
Currently, the three division champions receive the top three seeds, with the wild card team receiving the fourth seed. The teams are bracketed by the following criteria:
- The division winner with the best record will play the wild card, and the other two division winners will play one another, UNLESS:
- This bracketing would cause two teams from the same division to play in the first round. In that instance, the team with the best record plays the division winner with the worst record, and the other division winner plays the wild card.
Criticism of schedulingEdit
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 primetime at 8pm ET/5pm PT to generate the highest TV ratings. As a result, West Coast teams generally have to play on the road at 1pm ET/10am PT when many of their fans are unable to watch the game because they are at work or school. 
Oakland Athletics general manager Billy Beane has been critical of the seeding of the Division Series. He has called for the Division Series to be seeded strictly by regular-season record without regard to whether a team has won its division.
Had Beane's proposal been in place in 2006, both leagues would have seen Division Series matchups between a division champion and a wild-card team from its division, which is impossible under present rules. If it had been in place in 2004, the wild-card Boston Red Sox, with the second-best record in the American League, would have had home-field advantage in the Division Series over a division champion, which is also impossible under present rules.
- ↑ Street, Jim (2006-10-04). Mailbag: Was Penny the right choice?. MLB.com. Retrieved on 2006-10-07.
- ↑ Kroner, Steve. "Blame it on TV — but not always Baseball, too, wants top draw for prime time", 'San Francisco Chronicle', 2005-10-14. Retrieved on 2006-10-07.
- ↑ Verducci, Tom (2006-10-06). Beane has his day. Sports Illustrated. Retrieved on 2006-10-11.