Anyone who watched the key 4th-and-goal stop keyed by Alex Brown in the Bears-Eagles game is aware of how good Brown can be against the run.  I've seen Brown be a major force agaisnt the run the entire year.

ESPN gave some empirical evidence to back up my anecdotal assumptions.  

http://myespn.go.com/blogs/nflnation/0-3-225/Inside-the-number-of-Titans-Bears.html

• Chicago's highly-ranked rushing defense stuffed the Titans backfield of LenDale White and Chris Johnson. Tennessee rushed for only 20 yards -0 one yard off the franchise low. The only direction the Titans found any "success" was to the right.
  
  

  Titans running game by direction Run over Attempts Yards Left end 5 -7 Left tackle 6 -5 Left guard 1 -2 Middle 4 -1 Right guard 2 4 Right tackle 8 26 Right end 3 5

Overall, they had 11 runs for minus-12 yards to the left, seven runs up the middle for a total of one yard and 11 runs to the right for 31 yards.

While other factors could be at work -- where the linebackers and safeties play, for one -- the most consistent aspect of the defense is where the DL lines up.  RE Alex Brown lined up against the left side the whole day, and helped keep the Titans in negative rushing yardage.

Now if he could only get to the passer with that dominance...