Del Rio is not a bad coach;
he was hampered in J-Ville by an incompetent GM. It's near impossible to build a good team when your personnel decisions - including the draft - are dog shit. Del Rio was coach from 2003-2011 (fired in Nov. in 2011).
Look at the horrible drafts they had in that time.
http://www.pro-football-reference.co.../jax/draft.htm
A few good players here and there, but for the most part, even their first round picks were horrid. Matt Jones, Blaine Gabbert, Derrick Harvey, Reggie Williams.....plus almost no one decent after their first rounders. Drew-Jones was one of the very few hits in that span. You can't win with drafts that terrible. I think he is on a good track in Oakland. He has changed the team philosophy into a winning culture.