And yet we had a RB do a great job for the last 20+ years....Per the race issue here -- You need someone that has a feel for the whole game. Linemen and RBs only know a limited part of the play book. Same for defense - someone that knows the whole part of the defense AND knows something about what the offense is doing. I am not sure, but seems like the group that knows the most are white (qbs for sure) and the LBs perhaps. Then you need someone that is comfortable speaking to a crowd (although a crowd over the radio!).