The Cowboys have just signed Zach Thomas (LB). Multiple concussions slowed him down tremendously last year (only played in 5 games). Prior to last year, from 2001 to 2006, Thomas averaged 156 tackles each season. In 2006, the Dolphins had the 5th ranked rush defense. Last year, they had the worst rush defense. Even though he’ll be 35 years old when the season starts, Thomas should still hold his own and improve an already solid Cowboys rush defense (ranked 6th in 2007).