I always thought last year he got away with quite a few mistakes, for one reason or another. Things like interceptions that were dropped, or guys like Edwards and Winslow making tough catches on passes a lot of QBs wouldn't have thrown.
There's also some sentiment that whenever a game has mattered, Anderson has folded under pressure. Last year's game against Cincinnati in week 16, which was basically win and they're in, is an example of that. The game against Washington, which would have put them at 3-3 and back in the playoff mix was another example. Games that Anderson has done well in have generally been games where a lot wasn't expected.
Then again, Braylon Edwards should be giving about half of his check to Derek. Good lord has that guy been a bust and a half this year. When Syndrick Steptoe and Steve Sanders are your 2nd and 3rd receivers (Sanders going from practice squad to 3rd receiver in the span of 5 minutes) you're also not getting much help.