To understand the depths of animosity between the Miami Heat and Boston Celtics entering this year's NBA Eastern Conference finals, you have to go back to an otherwise nondescript regular-season night in March 2013.

That night in New Orleans, a Heat public relations official approached the team's traveling media contingent with a message from team president Pat Riley that would immediately go into the annals of history.

"Danny Ainge needs to shut the f--- up and manage his own team," Riley said, via that hand-delivered statement. "He was the biggest whiner going when he was playing and I know that because I coached against him."

For Riley, of course, the animosity wasn't just about Ainge criticizing then-Heat star LeBron James and his tendency to complain about officiating. Riley's beef with Ainge, and the entire Celtics organization, was personal.

While he has spent nearly three decades as the godfather of Miami Heat basketball, lording over one of the league's most successful and stable franchises, Riley cut his teeth as a player and coach with the Los Angeles Lakers, and spent many years duking it out for championships with their rivals in Boston.

As Riley's Heat have consistently stationed themselves among the East's elite over the past two decades, the team most often pitted against them has been the Celtics. As Miami makes its eighth trip to the East finals over the past 18 years and Boston makes its seventh when the two teams square off in Game 1 on Tuesday at FTX Arena, that shared history helps inform what could lie ahead.

Everything ties back to the summer of 2007, when the Celtics traded for Kevin Garnett and Ray Allen to play alongside Paul Pierce. Boston won the 2008 NBA title and returned to the NBA Finals two years later. But that's only part of the story. The Celtics' star-powered ascent to the top of the East played a pivotal role in James and Chris Bosh choosing to take their talents to South Beach to join Dwyane Wade there in the summer of 2010.

Boston took down James and the Cleveland Cavaliers in the second round in both 2008 and 2010. Pierce outdueled James in Game 7 in 2008, and then caused James to have one of his two worst playoff series of his career -- along with the 2011 NBA Finals -- to stun the top-seeded Cavaliers in 2010. One round earlier, Pierce hit a buzzer-beater in Game 3 to all but send the Heat home for the summer.