O'Brien didn't use his limited scholarships on OL & DT
That might have been a good short term decision but a bad long term decision. Freshmen and sophomores often contribute at skill positions but OL and DTs usually need a few years to grow.
Gaia, Dowrey, & Johnson in 2012 (18 total)
Hartman, Nelson & Mahon in 2013 (17 total)
Brosnan, Sorrell, Wright, and White in 2014 (23 total)
It takes 14 players to create a 2 deep chart at OL and DT. We only got 10 in those 3 years and Mahon was the only 4* recruit. That's why we're still a few years away IMO.