1) 1949: Number of playoff teams expanded from six to eight; bracket split by East and West conferences

In its inaugural season, ’46-’47, the NBA (then called the Basketball Association of America, or BAA) had two conferences (then called divisions) with 11 total franchises, 10 of which were chartered by hockey team owners looking to fill their arenas on off nights. It thus made sense that the NBA instituted a playoff system similar to that of the NHL at the time, wherein six teams qualified with the conference winners getting first round byes (the conference winners oddly then played each other in one semifinal). This system remained in place in 1948 even though the league was reduced from 11 teams to eight but in 1949, when they expanded to 12 teams, the playoffs followed suit. Four teams qualified from each conference and, for the first time, played each other within conference affiliations in the first two rounds. An East and West conference champion were hence declared for the first time (Washington Capitols and Minneapolis Lakers, respectively, in 1949) and faced off in the NBA Finals. This heavily predated the modern era of American pro sports postseason formatting, with the NHL, NFL, and MLB eventually following suit in the late ’60s.

2) 1954: Number of playoff teams reduced from eight to six; round robin instituted for first round

When the BAA and National Basketball League (NBL) merged in 1949 to officially form the NBA, there were 18 teams in the ’49-’50 season as a result of the unification. That quickly reduced to just 11 franchises in ’50-’51 and then down to nine heading into the ’53-’54 season. Looking to avoid a scenario where just one team missed the playoffs, the NBA owners agreed on an elegant solution for the postseason structure. The top three teams from each conference would qualify and face off in a four-game round robin against each other. The top two teams out of the round robin in each conference then matched up in a Conference Finals, with the winners taking on each other in the NBA Finals. In an interesting development, the Knicks lost all four of their round robin games despite finishing with the top record in the Eastern Conference regular season. Even though the league was contracted even further in ’54-’55, from nine teams to eight, the owners agreed to return to a more traditional playoff format going forward. In addition to its unique format, the 1954 postseason was also notable as the first to feature only franchises that are still active to this day.

3) 1958: Conference Finals extended to best-of-seven format
4) 1961: Conference Semifinals extended to best-of-five format

Up until 1958, the NBA Finals was the only postseason series in a best-of-seven format. But as the NBA saw an explosion in popularity in the late ’50s and early ’60s, thanks to a huge influx of star talent, the league decide to schedule more games in the lower series. It started in 1958, when the Conference Finals (then called the Division Finals) were broadened from best-of-five to best-of-seven. Ironically, both the East and West Conference Finals in 1958 ended in five games anyway, with both the Celtics defeating the Warriors and the Hawks besting the Pistons four games to one. The first Conference Finals to last the full seven games came a year later, with the Celtics defeating the Syracuse Nationals four games to three in 1959. In 1961, the Conference Semifinals were expanded from best-of-three to best-of-five, which would last for just six years until it was expanded again, to best-of-seven, in 1967.

5) 1967: Number of playoff teams expanded from six to eight; first round byes eliminated
6) 1975: Number of playoff teams expanded from eight to 10; first round byes re-added

With the chartering of the Chicago Bulls franchise in the ’66-’67 season, the NBA had 10 teams again for the first time in 13 years. This allowed the league to open up two more postseason spots, granting bids to the top four teams in each conference, leaving out only the last place teams. Chicago actually qualified for the playoffs in their inaugural season, getting swept by the top seeded Hawks in the Western Conference Semifinals. Like all the other major U.S. pro sports league, the NBA expanded rapidly in the late ’60s and early ’70s in response to population and economic explosions across the country. Between 1966 and the addition of the New Orleans Jazz in 1974, the league had more than doubled to 18 franchises, which were now split up into two divisions within each conference. To accommodate the inflation, the NBA expanded from eight playoff teams to 10 in 1975 and implemented a playoff system quite similar to the one currently employed by the MLB. The #4 seed and #5 seed in each conference faced off in a best-of-three “first round” series, with the winner advancing to play the top seed in the Conference Semifinals.

7) 1984: Number of playoff teams expanded from 12 to 16; first round byes eliminated

Following the ABA merger and the addition of the Mavericks as an expansion franchise, the NBA had 23 franchises in the early ’80s. It was also undergoing a second popularity boom, thanks to the proliferation of cable television and the public fascination with Magic Johnson and Larry Bird. These considerations led to an expansion from 12 playoff teams to 16, and the first round series were extended to best-of-five. This meant that 1983 was the final NBA postseason, possibly ever, to feature a bye or a best-of-three series. There was a notable first round upset in the new format in 1984, with the defending champion 76ers, as a #3 seed, getting stunned by the Nets. It took a decade for a top seed to be upset in the first round, with the Nuggets upending the SuperSonics in 1994. This opening round was officially referred to as the “First Round” up until 2004, when the NBA began calling it the “Conference Quarterfinals.”

8) 2003: First round series extended to best-of-seven format

Like most American capitalist enterprises, the story of the NBA in the 21st century is that of an entity striving to wring every last dollar possible out of its consumer base. Even if you want to argue that extending the first round to best-of-seven in 2003 was a move to simply ensure the better team more regularly advances, you have ask yourself why that’s in the best interests of the league? Not that we’re complaining about extra basketball. Interestingly enough, there were no upsets in the first round in 2002, the last year it was best-of-five, not even a minor one, with the higher seed advancing in all eight series. Then in 2003, under the best-of-seven format, there was almost a monumental stunner, with the top seed Pistons overcoming a 3-1 series deficit to hold off the Magic.

9) 2016: Teams with eight best records per conference qualify, regardless of division standings

One of the most thrilling and intriguing postseasons in NBA history, the 2016 playoffs featured buzzer beaters from Kyle Lowry and Damian Lillard, the Raptors reaching the Conference Finals for the first time ever, the 73-win Warriors shocking the Thunder with a 3-1 series deficit erasure in the Western Conference Finals and then LeBron James and the Cavaliers summarily stunning Golden State in a breathtaking NBA Finals. There was a more mundane but still significant development in the 2016 playoffs, one that ended years of controversy. In ’04-’05, when the Charlotte Bobcats joined the league, the NBA re-aligned into three divisions in each conference and granted an automatic playoff berth and top three seed to each division champion. This was almost immediately disavowed, when the Nuggets received a #3 seed in 2006 despite having the West’s eighth best record and the Clippers purposefully lost their final game to match up against Denver in round one. Starting in 2007, the division winners instead were only guaranteed a top four seed but this still led to some nonsensical situations. This was finally rectified in 2016, with division winners not receiving an automatic top four seed and not even receiving an automatic berth, as the top eight teams in the conference are seeded, regardless of division. Even with this fairer format now in place, many fans and media members have called for the elimination of conference playoff alignment entirely, advocating for the top 16 teams to be in the playoffs regardless of affiliation.

10) 2020: Play-in series instituted
11) 2021: Play-in series expanded to play-in tournament

In early June of 2020, the NBA league owners and Players Association agreed to restart the ’19-’20 season in late July after a nearly five-month hiatus due to COVID-19. Only 22 of the 30 teams would be living, practicing, and playing entirely within a sanitized “bubble” on the campus of Walt Disney World in Florida. With the remaining schedule also truncated, the league came up with the idea of a play-in series that would allow all 22 teams to have a better chance at a postseason berth. If the #9 seed in either conference was within four games in the standings of the #8 seed, those seeds would face off in a play-in series. The higher seed only needed to win one game out of two, while the lower seed would have to win twice in a row. This was a non-starter in the Eastern Conference, where the ninth seeded Wizards lost seven of their eight bubble games to fall well off the pace but it did create some excitement in the final days of the regular season in the West. Ultimately, it was the Blazers and Grizzlies facing off, with the Blazers winning the first game to clinch their playoff spot. Sensing yet another opportunity to expand revenue opportunities (and struggling financially in the wake of the COVID economic crisis), the NBA owners approved an expansion to a play-in tournament in ’20-’21. In this new format, the #7 through #10 seeds will face off to determine the final two playoff spots in each conference, utilizing what’s commonly referred to as the McIntyre System format. While many high profile players, including LeBron James, have griped about the new play-in tournament, don’t be surprised if it’s here to stay and gets permanently codified in the NBA playoff format going forward.