Last year, he was significantly worse than the guy who got fired, so I'm not sure what people were expecting. Seems to me like the same sort of "No player has more potential than the backup QB" situation that we saw with Skyler, where every preseason there was all this talk about how impressive he was, and in the regular season (and the playoffs!) he just shit the bed over and over.
There is a difference between looking good in the preseason against back up players and then shitting the bed against starters in the regular season and looking good against starters in the regular season and then shitting the bed against the backup in preseason.
The first is pretty normal because you are playing against weaker players and then stronger. The second shouldn't happen unless the player gets injured or something really odd happens.