Durability is a major issue for any professional athlete. It should be thought of as an ability, like speed, hand-eye coordination, etc. You can take care of you body and help, but at a core level, some people's bodies are more durable and some not so much.
I am starting to be a little concerned about Brown, but only a little. It is too bad that after a really big step forward last season, he is kind of taking a smaller step back this season. I still expect a long and successful career.