It's what we all knew, but there is some sort of perverse, and even scientific, satisfaction in seeing exactly where Sanchez stacked up, and the company he kept when looking at the worst regularly starting QBs in the league. Most of this data is pulled from Pro Football Focus which uses innovative stats that factor out some of the factors receivers bring such as drops.
The data here is organized by rank, and the rank is given a negative number so that being lower puts you lower on the graph. As mentioned, most of this is from PFF and is drawn from players in the top 50% of snaps taken. Only 27 players qualified so 27th is last in the league. The DVOA number is with a 100 pass minimum. As can be seen by Sanchez's Green line no QB who regularly played performed as poorly across the board as badly as Sanchez did. Weeden is the only QB that is close, but Weeden's Accuracy Percentage (suggestingly that he suffered some from teammate drops) and his Play Action efficacy put him above Sanchez, as does his QB rating when having the luxury of 2.6 seconds or more in the pocket.
What is interesting is to see among all these bad QBs displayed together that each of them do have some statistical strengths. Ponder is a poor QB, but he does have a pretty healthy accuracy percentage, for instance, and given time in the pocket he does pretty well. Notably Vick is a QB that seemed to share pretty much the same weakness profile as Sanchez this year (though not ranked as low throughout), with the exception of a high QB rating with 2.6 seconds or less in the pocket. There is an important caveat about Vick regarding QB pressures below.
What would not fit on this graph was Mark's Accuracy % on Deep passes. Here he was 20th in the league. While not even league average, at least it was better than most of the worst (only Luck was better at 13th in the league). Also there are three QBs that had the built in excuse of facing a high frequency of pressure on drop backs. Pressure can explain a lot. Vick was pressured 42.9% of the time, leading the league, and Luck 2nd most at 39%. And Freeman was 8th most pressured. Mark, Weeden and Fitzpatrick had no such excuse. Mark was 8th best protected QB in the league (whether by line play or play call), Weeden 6th and Fitzpatrick 4th.
It would seem that Sanchez has only really two peers at the very bottom of the league, Brandon Weeden a 29 year old former baseball player and now rookie, three years older than Mark, and Fitzpatrick who seems to handle questions of accuracy and pressure much better than Mark does...in a sense Mark Sanchez has no peers this year, a year of crushed confidence.
The statistical story with Luck is an intriguing one since he is what maybe in the early days we hoped Sanchez would be. His high Total QBR (a vote for the substance of this mysterious ESPN stat), the high degree of pressure he faced and his performance with time in the pocket point to a potential that nobody else in this group has.