Dirk Nowitzki is one of the greatest to ever play the game of basketball and that's not just because of what he can do on the court. Nowitzki's longevity as a player might be his most impressive feat. Next season, at 39 years old, will be his 20th season in the NBA . Few players can remain in the league that long and stay as consistently effective as he's been to achieve that sort of career feat.

Last season, Harrison Barnes joined Nowitzki and the Mavericks with hopes of becoming just as successful a player. One day at practice, Barnes brought up Nowitzki's incredible career and asked if he might be able to do the same. Nowitzki kept it honest. More, via the Dallas Morning News:

"Honestly, I've just been trying to work as hard as I can and spend as much time as I can with him in the gym. I remember one day at practice we're standing on the sidelines on the gym and said, 'Oh man, Dirk, you're about to get to 20 years. That's impressive. Do you think I can get to 20 years?' He's like, 'No way man. You need major skill to get to 20 years.' So that's kind of the nature of our relationship."

It's pretty clear that Barnes bringing this up is meant to be in a joking manner, but at the same time Nowitzki isn't wrong. The skill that's necessary to play 20 years in the NBA is something that few players possess. Never mind the health and shape that's necessary for just a regular NBA career. Once age starts to factor in there are some players that just can't adjust and eventually fall off. Nowitzki didn't let that happen to him and now he's one of the greatest to ever play. Hopefully the young Barnes heard that message loud and clear.