I love what Nolan has done with the D -- an upgrade at DL will make this a formidable unit. However, Nolan is clearly missing the requisite nuance and experience to create an effective offense. The two most important positions (QB and OC) are in shambles, and it's because Nolan failed to have a backup plan in each instance.
(1) Too much trust in Alex's quick development, and therefore not having a reliable backup QB. Even Nolan himself said that Alex was young and needed time, but then he puts all his eggs into that basket in year 3? Reckless.
(2) Too much trust in Norv Turner's "I'm here for a long time" promise, and therefore not having a legitimate backup plan. I mean, come on, he's a veteran ex-head-coach who clearly had an itch to run a team again. Nolan should've been prepared for the inevitable.
When you've got a young inexperienced tandem at QB and OC, there is NO WAY that an offense survives. Absolutely doesn't happen.