On one side, you've got the cocky young kid, who knows a lot but not as much as he thinks he does.
On the other, you've got the old grizzled veteran who is trying to hold on to the last strands of glory.
In the movies, they develop a father/son type of relationship, where the young kid embraces the veteran's discipline, and the veteran is re-invigorated by the kid's youthful exuberance.
In reality, the two just rub each other the wrong way. We've all had co-workers that we've hated, and NBA locker rooms work a lot the same way.