From the first season, 1947, of the NBA (called the BAA until the merger with the NBL in 1949) the top three teams from the Eastern and Western divisions were invited to the playoffs. The two division champions played a Semifinal best-of-seven series for entry into the finals. The other four teams played two rounds of best-of-three playoffs to face the winner of the Semifinal match. That year, the Philadelphia Warriors defeated the Chicago Stags four games to one in the first ever BAA Championship.
In the 1949 playoffs, an additional team from each Division was added, eliminating the byes, and two rounds of best-of-three series were played, followed by a best-of-seven championship. In 1950 the Minneapolis Lakers became the first champions of the newly named NBA, knocking off the Syracuse Nationals in six games.
The 1951 through 1953 playoffs changed the Division Finals into a best-of-five playoff. In 1954, the year the Indianapolis Olympians folded, the NBA Playoffs used a Round Robin for the only time in its history. Then, from 1955 to 1966 year, the league returned to the original six-team format, expanding the Division Finals to a best-of-seven in 1958 and the Semifinals to a best-of-five in 1961.
In 1967 the field was again expanded to eight teams, filling out the three-round bracket. A year later, the Division Semifinals were changed to best-of-seven playoff. Then, in 1975 and 1977, respectively, a fifth and sixth team were added to each Division, necessitating an additional First Round of best-of-three series.
Finally in 1984, the tournament expanded to its present 16-team format and the now-complete First Round was changed to a best-of-five playoff. In 2003 the first round was changed to also be best-of-seven.
Beginning with the 2004 season, with the addition of the thirtieth NBA franchise, the Charlotte Bobcats, the NBA realigned its divisions. The result was that each conference would have three divisions of five teams each, and the winner of each division was guaranteed a top-three playoff seed. This would change slightly after the 2005-06 season; while division winners still receive automatic playoff berths, they are guaranteed a top-four seed, as described above.
From the Beginning for next season, expanding the First Round returned to the best-of-three series, the Conference Semifinals best-of-seven series and the Conference Finals. It same with the current version will be necessary.
The previous playoff format, in place for the 2004–05 and 2005–06 NBA Playoffs, after the NBA was re-aligned into six divisions, created controversy during the 2005–06 season and playoffs, and would be changed prior to the 2006–07 NBA season.
NBA division winners were seeded higher than any other playoff participants, regardless of their record. Prior to 2004, when the NBA was aligned into two conferences with two divisions each, the top two seeds in each conference were reserved for the division winners. This meant that top two teams in a conference (by record) would be seeded either first and second (if they were in opposite divisions) or first and third (if they were in the same division). Because of the NBA playoffs’ preset match ups in the second round, this meant that the top two teams in a conference could never meet until the Conference Finals, assuming they both made it to that round.
After the NBA realigned its two conferences into three divisions each, the seeding rules remained largely unchanged. The top three seeds would now be reserved for division winners. This meant that if the top two teams (by record) in a conference were in the same division, they would be ranked first and fourth, and would face each other in the Conference Semifinals, instead of the Conference Finals, if both teams won their first round series.
In the second year of this format, the 2005–06 NBA season, the San Antonio Spurs and Dallas Mavericks of the Southwest Division did just that. This turn of events led to the playoff format being criticized by many. Critics claimed the match up was not only unfair to the team that would lose earlier in the playoffs than it deserved, but also created an unfair advantage for teams in the 2-7/3-6 half of the Western Conference playoff bracket, which could advance to the conference finals without playing either of the two best teams in the conference.
The Phoenix Suns, winners of the Pacific Division and possessors of the third best record, were seeded second, and the Denver Nuggets, winners of the Northwest Division and tied for only the seventh-best record in the conference, were seeded third.
The Memphis Grizzlies and Los Angeles Clippers met in the second-to-last game of the regular season, after the top four seeds had been clinched. The two teams were already determined to be the fifth and sixth seeds, and had only to determine which rank higher. The fifth seed would likely need to defeat the best two teams in the conference without home-court advantage to advance to the conference finals, as it would face fourth seeded Dallas, and likely face first-seeded San Antonio if it managed to defeat Dallas. The sixth seed would play Denver in the first round and would have home-court advantage, and only have to play, at most, one of Dallas or San Antonio—in the conference finals.
This led to speculation about whether the Grizzlies or the Clippers would have much commitment to winning their match-up in the second-to-last game of the season, since it was clearly most advantageous to lose the game in order to obtain the 6th seed. The Clippers eventually lost to Memphis without much evidence to refute the speculation that the Clippers had lost intentionally.In the first round of the playoffs, the Clippers defeated the Nuggets in five games, and Memphis was swept by Dallas. Ultimately, Dallas and San Antonio did meet in the second round, with Dallas winning in seven games, and advancing all the way to the NBA Finals.