If Mike Davis really is ready to play, then why this? It's hard to pick the HBC's mind on this one, but if I had to guess I would say that he is hoping that Rank will come out and tear it up so the Gamecocks can let Davis rest his shoulder for most of the game. Spurrier did say that Davis would play early, but I'm sure the senior could use the rest. And who knows? If Rank plays well, he could emerge as an important part of the team. The junior has played well so far this preseason, and it would be good to see a second back emerge in this game.
Also, unfortunately it looks like Casper Brinkley is out of a job. Best of luck to Casper in the future.