There were also a couple of reports before the draft, one posted yesterday, where a GM or scout felt that Frederick was the best in-line blocker in 5 years, and another a few weeks back that said Frederick is a better prospect than Kevin Zeitler, who went in the 1st last year. Now, I'm not in love with the trade back to take him, but I understand their reasoning for doing so. I think they thought he wouldn't last till their 47th pick.
They were already burned once before when they didn't have a 1st round pick because of the Roy Williams trade and saw Max Unger, a C they really wanted, get snatched up a few spots before the 52nd pick in '09. Perhaps they didn't want the same thing happening this year and were trying to assure that they got their man.