You are forgetting to take the whole team and the sport of football in consideration with Spiller. The packers might not have that great of an O-line but they are going to try to get stronger in that category even if it's not in the first or second round. One large reason grant can be as successful as he is, is our passing game. With as strong of a passing game as we have we can open up the running game. The opposing defenses can only concentrate on one or the other. With a back as dynamic and dangerous as Spiller in our back field that might just open our passing game up even more.
It works in the opposite direction too. The pass can open up the run and the run can open up the pass, hence play-action. Even if Spilller is gone I believe that Best can be that type of RB that can help us with this. In fact I think Best is the better receiver than Spiller. Spiller didn't really run a whole lot of routes at Clemson and had some questionable drops from the games that I saw. Still either one of these backs would be perfect to enhance our already potent offense.