Why did John Updike write "Ex-Basketball Player"?

I think that John Updike wrote this poem because he wanted to show how people who have a lot of potential and dreams can end up not doing what they wanted to do. Even if you are super good at something and think you may be doing it forever for the rest of your life you may not get what you want. You should always have a back up plan just incase your first plan does not work. Working hard in school could get someone farther in life than trying to be good at a sport.