Gregg Popovich's reign as an elite coach in the NBA has spanned over two decades now. 

The longtime Spurs head coach has been at the helm of arguably the most successful team in basketball over that time period, lifting five titles in 22 years in a golden era for San Antonio. 

He's mentored some of the all-time greats like Tim Duncan and David Robinson, and a series of other All Stars stretching from Tony Parker, Manu Ginobili and Kawhi Leonard, to the roster full of elite talent he now manages with Team USA. 

The 69-year-old commands respect around the game, and he's certainly earned it. 

'Pop's' unprecedented longevity of success with the Spurs has seen them make a ridiculous 21 straight postseason appearances, just one shy of the all-time mark set by the Syracuse Nationals/Philadelphia 76ers between 1950 and 1971. 

One of his longest serving and most trusted players, Tony Parker, has revealed some of the things that he believes has allowed his now former coach to continue to deliver success year in year out. 

Parker left the Spurs for the Charlotte Hornets this offseason after 18 years and four titles in San Antonio, and in his touching 'Thank You, San Antonio' piece on The Players Tribune he opened up on his longtime head coach and what makes him so special. 

“It’s hard to explain what makes Pop such a special leader." Parker wrote.

"Of course, there’s the stuff you know: He’s a genius communicator, a sharp Xs-and-Os thinker, a brilliant motivator, and an all-around great guy. But I think what makes him unique as an NBA coach are his principles: the way that he established them from the start — and then the way that he has stuck to them ever since,”.

He continued praising Popovich; “And that’s just Pop, man. That’s what makes him so special. It’s no B.S. when he’s giving you these words of encouragement … and it’s no B.S. when he’s giving you these words of criticism. When he’s starting you, when he’s benching you, when he’s handing you the keys to the offense, or even when he’s shopping the keys around in free agency to someone else … man, you’re still getting the same Pop, operating on the same principle, every time. And that principle is: anything that happens on his watch, it happens for one reason and one reason only. The good of the Spurs.”

It's safe to say Parker will forever be an admirer and close follower of his former coach, and it's not hard to see why.