When I think about the way you want a defensive line to play in the defensive scheme the Cowboys use, I think about a pack of dogs. Individually, each dog is vulnerable, but as a pack, the whole is greater than the some of their parts. I think this is the mentality that Rod Marinelli, Jason Garrett, Will McClay, and the Joneses, want to instill in their rushmen. That relentlessness and constant hunger, feeling like they're fighting every day just to survive, combined with the aggressive nature of the rushmen techniques preached by Marinelli,
However there is one more vital piece of the pack of dogs, that I don't see on the Cowboys' roster at this point. That piece? The Lead Dog, the Pack Leader.... the one guy who sets everything else in motion, the one all the other dogs are subordinate to, and they are fine with it. That guy is the leader in the classroom, on the field, and outside of the facility. In a pack, he's the one who goes out and fights the big battles, and on a football team he's the guy that makes the big play, the 3rd down sack, or the strip sack late in the 4th quarter to give the ball back to your offense to complete a comeback or ice a game.
That is why fans who were OK with the Cowboys decision to release DeMarcus Ware last Monday, citing a new approach to cap management, were upset when they failed to re-sign, (or seem to make an effort to re-sign) the player Rod Marinelli nicknamed Big Daddy in the rushmen meeting room. As much as DeMarcus Ware was the big name and highest-paid player along the Cowboys defensive front, Jason Hatcher seemed to be the lead dog. His play set the pace for the defense; when he played well, so did the rest of the D, when he disappeared, the opponents side of the scoreboard was in for a workout.
In my opinion, this is why the Cowboys have spent the last 48 hours courting the two best remaining free agent rushmen. Both Henry Melton and Jared Allen have the ability to be that alpha male, the lead dog up front. Having either of those players up front removes a great deal of pressure from the team leading up to the draft in May. I only view three guys in the draft who are pure defensive linemen, who would have the ability to be that Alpha right out of the blocks, Jadaveon Clowney, Aaron Donald, and Timmy Jernigan. Outside of those three there are a lot of quality players, but no one who is ready to come in and be the man right away. Beyond that, Jernigan projects as a 1-technique "Cocked Nose" that the Cowboys, both publicly and through their actions last year (see Sharrif Floyd) seem hesitant to pick in the first round. That leaves two guys, Clowney, who will likely be gone 10 or more picks before the Cowboys are put on the clock, (and no they won't trade up for him), and Donald, who is about 50/50 to end up available at Dallas' #16 pick.