I have a lot of time and a lot of respect for Pro Football Focus, the research and statistical analysis they do should be commended, they have brought baseball style sabermetrics to football. Saying that, Baseball and Football are two completely different sports! and I think baseball can be justified and explained with stats than football. However saying that, PFF posted an article tonight that although not surprising, is rather worrying.
Sanchez was pressured 164 times, was sacked on 23.8% of those, has a 0.60 touchdown to interception ratio and completed 36.4% of his passes for the worst grade of -25.1. To add a little context -7.1 is the league average and Eli Manning came in at 9.8.
They limited the variables by restricting the measures to QB performance only, rather than WR or RB mistakes as explained:
This is more than just looking at the raw numbers, but looking at the context of the throws made. A positive completion percentage may show a QB dumping a ball off on third down for a short gain that sees the punting team coming on the field. Our grading can look at a quarterback evading pressure, throwing a perfect ball, only for it to be dropped–yet still rewarding the QB for his excellent play. It’s why we’re confident when we say over the balance of this year, there hasn’t been a better QB under pressure than Eli Manning. Here’s the entire list.
Take from it what you will, but it's well worth a read a few minutes of consideration.