Oher graded out 75th of 84 qualifying tackles in 2014, per Pro Football Focus, which rates player performance.
http://profootballtalk.nbcsports.com/2015/02/05/titans-waive-michael-oher/
Yep. Also per PFF, his only good year was his rookie year in 2009. Bouncing back and forth between LT and RT. No G experience. The PFF grades say that he's a poor pass blocker and a really poor run blocker, which tells me he'd be a poor fit at G.