Updated to include getting debacled by Cincy. Since my stats post on the O-line was so popular (19 comments!) /sarc, I'll do the same for our defense and d-line.

By conventional stats, the Bears are 13th 16th in yards per game, 14th 16th against the pass, 6th 18th against the run, and 15th 22nd in points allowed. (above average) (not good)
They are 13th 6th in yards per play (good) and 28th 24th in 3rd down percentage (40% 44%) (real bad).
Other conventianal defensive stats:  10  11 sacks (21st 22nd), 7th  5th in int's (10), and LAST 22nd in recovered fumbles (2 3).
According to Football Outsiders, the Bears are 13th 21st overall in Defense DVOA.  11th  24th vs the pass, 20th 16th vs the run, and with a variance of 1.4% 5.9% (ranked 1st 19th) which means the Bears defense is no longer the most consistent in the NFL so far this season.  They've had no great games and no stinkers 1 HUGE stinker.

So what does all that mean?  The Bears D is little above below average.  They're not getting to the quarterback enough, can't stop teams on 3rd down enough, and are not getting enough turnovers.

Let's dig a little deeper.

According to FO, our defensive line is ranked 5th 13th overall in Adjusted Line Yards (the Adjusted Line Yards formula takes all running back carries and assigns responsibility to the offensive/defensive line based on the following percentages: * Losses: 120% value, * 0-4 Yards: 100% value, * 5-10 Yards: 50% value, * 11+ Yards: 0% value).  Basically, they're doing a good average job against the run except in one area.

Their Power Success is 78% 69% against them for 26th 22nd in the league-still bad.  On 3rd and 4th down, with less than 2 yards to go, teams are converting 78% 69% of the time they RUN the ball.  That's just turrible as Charles Barkley might say.  Pretty good indication of why the D's 3rd down conversion percentage is so bad.

Predictably, the Bears D-line is ranked 20th 24th with a 6.1% 5.5% sack rate; they don't get to the quarterback, and they don't stop the run.

Let's dig even deeper on those disappointing Run Defense stats so we can assign some blame!  The table excerpt lists the opposing teams success versus the Bears based on where they run the ball.  (These runs are from the perspective of the OFFENSE, so a run listed as LEFT TACKLE is actually at the RIGHT defensive end.)


RNk TM        LEFT END     LEFT TACKLE     MID/GUARD     RIGHT TACKLE     RIGHT END
5     CHI        3.52      9        1.45      1               3.54      11        4.83      28               2.48      9

13   CHI        3.70     12       2.85     4               3.71      14        5.01       29              3.14       11

The Bears really struggle to stop runs by the opposing Right Tackle (our Left side), I'm looking right at you Tommie Harris (and Harrison).  With a dissapointing assist from Ogunleye and our revolving door at Strong Side Linebacker. 

With this obvious weakness to our run game, does the opposition try to exploit it?  Here's the opposing teams' run breakdown against the Bears plus the league averages:

Rnk Team     RBCarries     LEFTEND     LEFTTACKLE     MID/GUARD     RIGHTTACKLE     RIGHTEND
5      CHI        106                 14%                  14%                    38%                    17%                       17%

                        149                 12%                 18%                    35%                    16%                       19%
x      NFL        x                       11%                  13%                   51%                    14%                       11%

The Bears opponents know the Bears' weakness and they are exploiting it.  Tommie Harris (our whole D-line really) is killing us, he can't stop the run, and he has ZERO sacks.   Ogunleye and whoever plays SLB are not helping much either.

Now, let's look at how the Bears pass defense is doing.
On the FO team defense page, they list opposing WR's DVOA against the defense.
Against #1 WR's the Bears are 23rd 30th, against #2's they are 14th, against 3's and 4's they are 3rd 9th, against TE's they are 6th, against RB's out of the backfield they are 12th 20th.

#1 Receivers we've faced are Calvin Johnson, Hines Ward or Santonio Holmes, Roddy White, Greg Jennings, Ochocinco & either Housh or Burleson.  Basically #1's are hurting us the most.  Is this Bowman or Tillman?  My gut says Bowman because Calvin Johnson did his damage while he was covering him.  Greg Jennings did his while Vasher was covering him.  Roddy White did his while no one was covering him.  Ochocinco shredded them both.  With good numbers vs 3's, 4's, TE's & Rb's, our linebackers, safeties, and nickel are doing an adequate job.  Although, opposing TE's are doing a lot of damage in the RedZone vs us (see Atlanta & Detroit games).  I think the Bears decision to put Tillman on the other teams' #1 going forward will lead to improvement in this area (maybe not).  I hope to see Tillman shadow Esteban Ochocinco all over the field on Sunday.  I hope to see Tommie Harris on the sidelines, which is now happening.  What a difference a week makes, our D looked awful on Sunday and these stats obviously back that up.  #1 Receivers are absolutely killing us.  Our D-line is bad.  Lucky for the Bears, Cleveland doesn't have a #1 receiver anymore.  However, Arizona comes the weak after, look for Larry Fitzgerald to have a career day.