The 2011 Buffalo Bills are not unlike the 2011 San Diego Chargers. The difference is that the Chargers were hyped before the season as a very good team, which made it seem weird when they lost to every good team that they played. The Bills started off 4-1 (and then 5-2), and did it in exciting fashion (with late-game comeback wins against the Raiders and Patriots), making them overhyped as well.
Buffalo's slide in recent weeks (5 consecutive losses, 2-7 in their last 9 games) can be blamed on two things. Number one, their competition has gotten better. Instead of playing the Redskins, the Raiders (with Jason Campbell), the Chiefs (the game that Jamaal Charles was injured) and Eagles (still completely lost), they're not playing teams at exactly the wrong time. They've lost to the Jets twice, the surging Cowboys, the reborn Miami Dolphins and a Titans team that now has Chris Johnson running for 130+ yards a game again. Those are all teams San Diego could've lost to as well. With more games against the Dolphins and Patriots, and a matchup against the tough-to-beat Denver Broncos, this game against the Chargers might be the Bills only hope to get their 6th win this season.
The second point of blame for their slide is a nasty case of the injury bug. The Bills have lost their best Cornerback, Nose Tackle, Kicker and Running Back, as well as other important players (like Donald Jones and Shawne Merriman). For a team that is trying to rebuild quickly, it's probably too much to ask that they have starter-level talent to fill in at each of those positions when the first guy goes down.
So, why do I think the Bills will beat the Chargers on Sunday? Easy, they're not as bad as the Jacksonville Jaguars. When the Chargers pass-rush can't get to Ryan Fitzpatrick, he'll carve up the secondary in ways that Blaine Gabbert can only dream about doing at this point. C.J. Spiller is just the type of running back to make a couple of big plays in the running game against the Chargers, who aren't very physical or fast, as well.
The good news is that not all hope is lost. The Bills' pass-rush isn't very good, meaning Philip Rivers should have time to throw the ball again. If he can avoid mistakes (and he didn't in Jacksonville, there was that stupid pass to Antonio Gates that never should've been thrown) and make good throws downfield, the Chargers can build a lead and their lack of a pass-rush won't matter as much. However, if it's a close game or the Bills can build an early lead, the ball will be in there court against a San Diego team that is just as flawed (or "bad") as their own.