There has been a notable shortage of African-American baseball players in recent years. I can think back to 1980's and there were several excellent black players at all positions.
For whatever reason, fewer young black athletes are choosing baseball as a primary sport. As a result fewer players are competing for spots into the major leagues. The problem is that as some of the established veterans (ie Sheffield, Jeter, Carl Everett, etc), enjoy some success in MLB, eventually they will opt for retirement. Who will replace them?
As far as I can tell, there are only a handful. In fact, most of them play for the Florida Marlins.