On July 31, 2007, the Boston Celtics completed their 'Big 3,' by acquiring Kevin Garnett in a mega-trade with the Minnesota Timberwolves. Garnett was paired with Ray Allen, who Boston had acquired a month earlier, and Paul Pierce, who was already there.

Together, the trio went 66-16 in the regular season and won the NBA Finals in 2007-08. They got to the Eastern Conference semifinals the next season and back to the Finals in 2009-10, losing to the Los Angeles Lakers.

And while the legacy of winning a title and getting to two championships in three years is certainly a good legacy on its own, the true legacy of the 'Big 3' is actually much bigger than that. It helped re-define the NBA as we know it.

Everyone has always acknowledged that in order to win, you need a good team. That's just Basketball 101. However, it had previously thought that building out a great "Batman and Robin" duo was the proper way to build a winner. Often times, but not always, that duo was acquired via the draft and players grew together.

Think Michael Jordan and Scottie Pippen for the 1990s Bulls. Think John Stockton and Karl Malone for the 1990s Utah Jazz or Gary Payton and Shawn Kemp for the 1990s SuperSonics.

Jordan and Pippen were the gold standard for years, with teams trying to replicate what they had. Then, Shaq and Kobe Bryant won with the Lakers, still proving that a great duo was the way to go, but showing people that one member of the duo could be acquired by bringing in someone from the outside. Shaq had previously played with the Orlando Magic.

The 'Big 3' with the Celtics challenged that way of thinking, showing that a team could actually win with three superstar talents. A team could win despite having three egos to contend with, three big salaries to contend with and it could find enough shots for three marquee players while still keeping everyone happy.

With how good the Celtics were, teams began to load up on chasing their own 'Big 3.' 

A) They needed a trio that could compete with Boston directly

B) The blueprint for a championship was born

As a result, we saw the Miami Heat form a 'Big 3' with LeBron James, Chris Bosh and Dwyane Wade. That group won two titles, and birthed a rivalry with the 'Big 3' in Golden State, a homegrown group of Steph Curry, Draymond Green and Klay Thompson. That group eventually expanded to include Kevin Durant.

Ever since then, teams have worked to find their version of a "Big 3," either through drafting, trades or free agency. Durant, James Harden and Russell Westbrook in Oklahoma City are one example that also got to a championship series, though they were beaten by the Heat.

Because of the NBA's salary cap rules, it's harder to put together a true 'Big 3' anymore, but the Celtics found a way to win a title with Jayson Tatum, Jaylen Brown, Kristaps Porzingis and Jrue Holiday all making fairly big money.

Now, teams are somewhat going back to duos, as the money often necessitates this: Nikola Jokic and Jamal Murray in Denver, Tatum and Brown in Boston, and Kawhi Leonard and Paul George in Los Angeles.

But regardless of how it's being done now, the Celtics ushered in an era of player movement, player empowerment and re-defined the NBA culture. They were also immensely popular.