The NBA ruled several years ago that players needed to enroll in a year at college before going to the pros. This prevented players from following in the steps of Kevin Garnett and Kobe Bryant and entering the league straight from high school.
The rule has been a smash hit success, especially in the case of guys like Kevin Durant and Derrick Rose. In essence, players who probably weren't ready for the NBA in the first place went to college for a year and honed their games to the point where they could really compete with the best in the world.
In the case of some players, an extra year in school is probably less than what they need. Some players need two, three or four years. And some players probably just need to go back to school to avoid the horrors of starring for a bottom-feeding NBA team.
These three players should have stayed in school for at least another year. It could have saved them a lot of frustration.