Not trying to set you off, but I don't see the "home run" speed. I see him outrunning defenders with pedestrian speed from mediocre programs. But I also have seen him getting caught from behind just as often. His speed looks ordinary to me.
Not sure why he didn't work out today, but if he knows he's not going to run well, sitting out would be a logical move to preserve his value.
I think he'll be a very, very good NFL RB, because his tackle-breaking ability seems to be elite. But unless he's a truly exceptional prospect in the mold of Adrian Peterson, I'm not interested in taking him in the top 20, let alone at #9.