1) Who Will Stop the Run?
This week's game has two main components that have haunted the Bears in recent years. The first, and most recent one, was the 2013 version's inability to play anything resembling run defense, taking on one of the top-rushing teams in the NFL. Lamarr Houston and Willie Young were signed (and Ego Ferguson drafted) expecting to be big contributors in stopping the run, and they get a great test here.
2) The Pass Rush
The other was, until last year, the Bears' inability to stop anybody that breathes from breaking through or past the offensive line and sacking Jay Cutler. For an interesting stat, last year's Bears racked up all of 31 sacks - a hair under two per game. Kyle Williams, Mario Williams, and Jerry Hughes - the Bills' top three returning sackmasters, picked up 33.5 by themselves.
Notice how I included "returning" in there. They're baaaaaaack...
Fortunately, the Bears' pass protection looked infinitely better last year, and they'll need to continue that. They do return the same starting five, so maybe it'll be a little easier. But the Bills will be a good test in that regard. Mario Williams will be spending some time against Jordan Mills, so we'll see how that works.
3) The Return of Chris Conte
Marc Trestman's already stated the Bears are going to rotate their safeties, so this effect may well be overstated. However, how Conte looks coming back from surgery and a concussion will be interesting going forward, as long as he has a significant role on the team.
4) The Intermediate Pass
One of the things worrying me in the preseason (for whatever that's worth) was the window that kept opening up right behind the linebackers, but in front of the safeties. Teams seemed to find that hole and hit it with some regularity. Speaking with Matt Warren over at Buffalo Rumblings (if you haven't watched that 40 minutes of Bills/Bears discussion, you're missing out!), we found out that the Bills really love that hole, as it's one of the few things E.J. Manuel can throw to semi-accurately. Sammy Watkins and Marquise Goodwin can both get there; the Bears will need to be ready for both of them.
C.J. Spiller's also a good target out of the backfield, so having the speed of a Shea McClellin should play a role in bottling that up.
5) The Mismatches
Whatever you want to call them - the Chicago Skyline, Jeffries, whatever - Brandon Marshall and Alshon Jeffery are big, big targets that are open even when they're covered. And while the Bills' back four are talented, they pale in comparison to their guys up front, as well as the guys they'll be expected to cover. The offense runs through the passing game, and those passing game targets will need to come through. (Read: Alshon can't let that deep one hit both his hands and bounce away.)
6) The Bears' Own Pass Rush
Yup, the Bears have a pass rush too. At least for right now. We mentioned the heavy investment in stopping the run earlier, and that holds true, but getting to E.J. Manuel to prevent those deep/intermediate throws is awfully helpful as well. If the defense hopes to improve, they need production from Jared Allen, Jeremiah Ratliff and Will Sutton too. Ratliff picked up a sack and a half in his short time last season, so we'll see if a full offseason helps him out.
The Bills themselves are starting a rookie at right tackle, but it's a pretty decent unit left to right, including left tackle Cordy Glenn. It should be a good test of the Bears' own pass rush, too.