Being a Mormon, Jabari Parker has a duty to perform a mission to help spread the world of God for two years, and it would come after his freshman season.
If all were to go well with his career, that would conflict with him being an NBA player at age 19.
While I am not an expert in the Mormon faith, I do know that this mission is very important and may outweigh Parker's desire to be an NBA player.
However, if Coach K were to offer a way for him to play his freshman season, then do his mission and return to college to prepare for the NBA, Parker would be tempted.
This would be an ideal pitch for any coach, and Krzyzewski may have to make this offer in order to land such a great player.