I came across this article commenting mostly about how Flacco's W-L record is largely overrated, much the same way Sanchez's is - he breaks down what the expectation for other QBs would be based on the same performance from the same defense... A decent read - but he mentions David Carr and how he woefully underperformed (not surprising), but then he also mentions Fitz who is also one of the worst performers based on expectation - according to the author, Fitz should have accounted for about 4-5 more wins than he has in his Buffalo tenure...

http://www.grantland.com/story/_/id/8434708/the-numbers-never-lie-ravens-fueled-their-defense

"On the flip side, David Carr was dismal. Carr won just 23 of his 79 starts, virtually all of which came as a member of the Texans. Carr didn't have great defenses in Houston, but they were better than his performance, as their figures suggest that Carr "should" have won about 34 games, an 11-game swing. Among active quarterbacks, the worst candidate has been Bills quarterback Ryan Fitzpatrick, who won 18.54 games against an expectation of just under 23 wins."