The offensive line must get its mojo back

It was hard to watch the Steelers offensive line fail to run block last season. As good as they were in pass protection they were as bad as run blockers. As a group, they only rushed for 90.4 yards per game with was No. 30 in the league. How much of this was the loss of Mike Munchak or how much of it was just a lack of talent on an offensive line getting older? Honestly, it is probably a healthy dose of both.