Dallas Mavericks icon Dirk Nowitzki and Boston Celtics great Kevin Garnett have mutual respect for each other, but things didn't start that way. In fact, they hated each other.

According to Tim Cato of The Athletic, Garnett didn't like the way the Mavs star talked and what he'd say while on court. The feeling was mutual for Dirk, though, especially since KG was a renowned trash-talker himself. However, everything changed when Dirk developed his confidence.

As Dwayne Wilson and Chad Lewis–both equipment managers for the Mavs when Dirk arrived–recalled, Dirk talked back at KG and it was the start of the rivalry between two of the best power forwards in NBA history.

Per Tim Cato:

It wasn’t until Nowitzki began talking back to Garnett that they began developing mutual, if begrudging, respect.

Wilson often talked trash to opponents from the bench. It was a moment when Nowitzki stole one of his favorite lines that made him realize Nowitzki was growing up. In a game against Minnesota, Garnett fell down and Nowitzki, without hesitation, yelled, “Get your ass up, we ain’t through kicking your ass.”

“He finally got the confidence in himself to be able to go back at ’em,” Lewis says, “and that was a big part of his growth and maturation.”

Dirk Nowitzki had always been a competitive player, and while he had a rough start to his NBA career, he eventually developed to become the franchise player that the Mavs had always envisioned him to be.

Playing against the likes of Kevin Garnett, Kobe Bryant and Tim Duncan has certainly helped him as well, with the level of competition pushing him to strive to reach greater heights as well.

Nowitzki is the greatest Mavs player of all time, and one of the best to ever play in the NBA. And rightfully, his jersey retirement on Wednesday is a well-deserved recognition not only for his contributions to the team but to the whole franchise as well.