What's wrong with the Bills' D?

The Buffalo Bills made the biggest signing in free agency last offseason when they acquired pass-rusher Mario Williams, formerly of the Houston Texans. Williams, the top free agent on the market, signed a six-year, $100 million contract to help save a defense that gave up 27.1 points per game in 2011, 30th in the NFL. After eight games, however, things have only gotten worse. Even after holding the Texans to 21 points Sunday, the 2012 Bills are giving up 31.0 points per game, worse than anyone except Tennessee. Though Williams has definitely been a disappointment, he can't be blamed entirely for the collapse of the Buffalo run defense, nor for problems in the secondary that are limiting Buffalo's defensive options. But he hasn't helped much either.

The Bills hoped Williams would bring a big-play element to their defense, but he had little to offer in the first part of the year. At Football Outsiders, we credit defensive players with a defeat any time they cause a turnover, a loss of yardage or a stop on third or fourth down. In each of his past five seasons in Houston, Williams averaged anywhere from 1.2 to 1.5 defeats per game. Through seven contests in a Buffalo uniform, though, he had only five defeats.