You don't think man coverage on Thomas and Sanders, with Daniels and Davis up the seams, and Hillman in the backfield, isn't scary?
I love what Butler brings, but he had his hands full with Brandon Marshall. Demaryius Thomas is a step above Marshall, and Coleman looked like a lost man against Decker. Sanders has another level of speed that the rookie will have to deal with. Add a decent 2TE set and a competent RB and Manning is able to keep the slack off his noodle arm.
If Bill doesn't look for a legit #1 CB, it might be a long day in Denver. Not to say we don't have prominent offensive weapons ourselves, we do, but we certainly don't have a defensive secondary as lockdown as the Broncos have.