I asked Raider Nation which of the physical drills they valued most in a defensive back. The top vote getter was the 3 cone drill. Second among the options was the 60 yard shuttle. Here are the results of those drills in the 2012 combine.
3 cone drill
1. Nathan Stupar, Penn State- 6.84
2. Tank Carder, TCU- 6.89
3. Chris Galippo, USC- 6.90
4. Luke Kuechly, Boston College- 6.92
5. Audie Cole, NC State- 6.96
60 yard shuttle
1. Luke Kuechly, Boston College- 11.43
1. Tyler Nielson, Iowa- 11.43
3. Tank Carder, TCU- 11.53
4. Nathan Stupar, Penn State- 11.64
5. Demario Davis, Arkansas State- 11.65
Observations: Looking at this, it's pretty clear who the athletes are at the linebacker position this year. Tank Carder, Nathan Stupar, and Luke Kuechly all landed in the top four in both categories. But not a lot separates number one from number five in either category.