You just don't replace a 1st-round-draftee LT. See Ole Miss and their 'underperforming' year, and us post-gun/Bud-car-gate (Mike Brown?, anyway, not a first rounder, but same principle).
There will be an associated offensive drop-off. If much of the rest of the offense had already peaked (Relf, Ballard), then there will be a net drop-off. I will be happy to see WR improvement for a net effect of the same offensive performance as last year. Problem being, that we lost significantly at DE and LB too, so the D might not be as good either.
I'm expecting 8-4. Mullen is unlikely to lose the games we should win. Win one of AU, LSU, GA, and AL. Win one of SC and AR.
I guess it all comes down to, can the OL beat the DL of the rest of the West? I just don't see it yet, and i don't think the D is good enough to give Mullen enough of a chance to coach us over the gap. We'll be top 25, and if any team has issues we'll beat them (a la GA, FL last year), but we're just not a top 10 team yet, and that's what it now takes to win in the West.