For the same reasons that people here seemed to place to much blame for the subpar passing offense on Hill, Tanner was seen as having regressed.
I think it is much more likely that Tanner is closer to the Freshman version that had fans so excited and that the WR and OL issues that contributed greatly to the passing game looking poor all year was really a bigger problem than most fans are willing to admit or recognize.

I am worried about the offense again, but it has less to do with Mangum and more to do with the WR group not really changing a lot, I have more hope that the OL will be improved.