He only wants to run and chase and tackle from the side or back. He dances around until the play is behind him or someone else has taken on the ballcarrier headon, then he springs into action. Its why all his plays are 7+ yards downfield. I swear sometimes it looks like he vacates his gap when he realizes the RB may come through it just long enough to let him go by so he can try and chase him down from behind. Thats the only explanation I can some up with why he hides behind a DT instead of filling his gap. The coaches in Dallas realized this and finally convinced Jerry he couldn't play anymore and was killing the D. Now Dallas has 11 players trying to make a play instead of 10 and it shows.