A youth movement in Dallas has some veterans looking over their shoulders, particularly members of the defensive line.

Newcomers like defensive ends Sean Lissemore and 2012 third-round pick Tyrone Crawford are putting pressure on veterans like Marcus Spears and Kenyon Coleman, who have two decades of combined experience compared to the three combined years of Lissemore and Crawford.

The number of young defensive players on the Cowboys defense is more than most clubs. Of the 38 players currently listed on defense, 25 have three years or less of NFL experience, and 10 are rookies. In contrast, the Miami Dolphins have 24 defensive players with three years or less experience out of 41 players, and the Carolina Panthers have 22 out of 41.

Lissemore was drafted in the seventh round in 2010 and has progressed nicely ever since. In 2010, he appeared in only two games, but he appeared in all 16 games and recorded 28 tackles and two safeties in 2011.

Lissemore returned from an oblique strain that caused him to miss most off-season training camps this year, but the 24-year-old has reportedly impressed defensive coordinator Rob Ryan with his all-around skills.

"He's going to play everywhere," Ryan told the Fort Worth Star-Telegram. "We're moving him around in multiple spots. It increases his value for us on defense."

Crawford, a rookie out of Boise State, has received high praise from head coach Jason Garrett.

"Everything he does, he does it with kind of a relentless feel," Garrett said, according to the Dallas Morning News.  "And that's what we saw on tape, and that's what we're seeing from him in practice."

Meanwhile, veterans Spears and Coleman have proven to be durable. Spears joined the Cowboys in 2005 and has missed only eight games over his seven-year career. Coleman has played 12 NFL seasons, and the 33-year-old has only missed three games in his last six seasons.

Dallas could release one or the other and save $2 million in cap space, but it is unclear if the Cowboys favor cap flexibility over veteran leadership. The club doesn't have to make such a move, but may choose to if they want to extend their youth movement.

"It's always a possibility, man," Spears said. "I think for right now I'm in the blue and silver, so I need to pay attention to detail where I am right now. If that situation comes about with upper management and myself, then so be it, but right now I have to do what I have to do for the Dallas Cowboys."