A Running Back?

Scott, having read your latest Fab 5...don't take this wrong, but with the glaring needs we have but didn't address through FA at offensive and defensive line, why in the hell would we take a running back?  :o  No, our running backs are not spectacular and Martin has been dissappointing, but with a better line they certainly are servicable.  Sims shows promise, Rainey is solid even if average. We have but seven picks...  let's do qb, guard, tackle, and defensive end.  I can't believe I'm the only one who feels this way.  If not, what position are the Bucs willing to sacrifice in order to pick up a mid round rb?