FYP
The two are not mutually exclusive. Your version is, however, much less telling in that the claim is reduced to "worst starting quarterback since sometime last season". That doesn't exactly cover a lot of quarterbacks.
I also think you're wrong. Tavaris Jackson had a 70.8 passer rating last year and a 64.8 rating when he was benched this year (i.e. now). In his rookie season (started 2, played in 4), he had a passer rating of 62.5, almost exactly the same as Beck (half a point less). One big difference: Jackson actually had (and has) a good team around him. Beck had crap.