A legitimate argument can be made that the rivalry between Paul Pierce and LeBron James is the greatest one we have seen in recent years.

The two stars battled in the playoffs five times and clearly had a dislike for one another on the court while rarely even acknowledging one another off of the floor.

To this day, we don't even know if the rivalry was friendly, because neither player really even discussed their feelings for one another during media interviews.

What most of us also don't know is how the bad blood started.

It didn't occur during the first playoff meeting between the two players in 2008, when Pierce's Boston Celtics edged out James' Cleveland Cavaliers in a seven-game series victory. It didn't occur once James took his talents to South Beach.

It actually began at the start of LeBron's second season in the league in 2004, when Pierce and James almost came to blows following a preseason game at Ohio State, as ESPN's Brian Windhorst reminded Bill Simmons:

Both players were hit with technical fouls for an exchange during the game, and later on in the contest, Pierce spit toward the Cavs' bench and was fined $15,000 as a result.

Still, in spite of the fact that Pierce and James were not exactly best friends, they did have mutual respect for one another.

“I don’t think it is like or dislike, it is what it is,” Pierce said back in 2012, per Windhorst. “He’s been on some great teams, I’ve been on some great teams and we’ve had to face one another. After awhile it became a mutual respect for the things he’s done in this league and the things I’ve done in this league.”

James agreed:

“We understand how competitive each other are,” James said. “It’s always fun to go up against the best, and he’s one of them.”

This incident is just one of many to remember from this great rivalry.