Cowboys defenders hungry for more

SAN ANTONIO -- Proud general manager Jerry Jones can give two potentially great reasons as to why the Dallas Cowboys' defense can improve after allowing the fewest points in the NFC last season.

Those reasons are a couple of recent first-round picks: outside linebacker Anthony Spencer and cornerback Mike Jenkins.

Jenkins and Spencer were hand-selected by coach Wade Phillips to play opposite Pro Bowlers Terence Newman and DeMarcus Ware in the most important positions in his defensive scheme. The former pair had breakout seasons in 2009. But Jenkins and Spencer believe they've provided just a glimpse of their potential.

Spencer, the 26th-overall pick in 2007, said, "There's really not one place I can't improve."

Jenkins, the 25th-overall pick in 2008, added, "I can get a lot better."

A big grin breaks out on Jones' face when the subject of his young, blossoming defensive stars is brought up. He's fascinated by their talent, intrigued that they're still learning the intricacies of Phillips' scheme and encouraged that neither has given any indication during training camp that they're content after emerging as forces for a playoff team a year ago.

"Their evolving will make it a better defense," Jones said. "Because of who's on the other side of them, you get a little leverage off of them just being better out there at their positions. It creates a real matchup situation. You've got it coming from both sides."

Just how good were the 25-year-old Jenkins and 26-year-old Spencer this past season?

Jenkins picked off five passes -- and another one in the playoff win over the Eagles -- while earning a trip to the Pro Bowl as an alternate along with Newman. Per Stats Inc., opponents completed only 53 of 107 passes they threw in Jenkins' direction, gaining 643 yards with a passer rating of 53.6.

Forget about the numbers, though. All you need to know about Jenkins is that Phillips has given him the freedom to play press coverage pretty much whenever he wants. That's how much faith the Cowboys have in Jenkins' combination of long arms, speed, confidence and competitiveness.

Jenkins saw a technically flawed player who got lazy on a handful of snaps when he studied his film from last season. He plans to fix those issues while improving his knowledge of opposing receivers.

"He's not perfect, by any means," said Phillips, who is given freedom as a play-caller because of Jenkins' ability in man coverage. "But he is a shutdown-type cornerback."

Phillips has described Spencer as a dominant player against the run for the last two years. Tight end Jason Witten claims there isn't an outside linebacker he has faced who is more difficult to block. Linebackers coach Reggie Herring, who raves about Spencer's natural ability to read plays and react instantly, boasts that nobody can block Spencer on a consistent basis.

Spencer flipped the switch as a pass-rusher down the stretch last season after many near-misses while going sackless in the first 10 games. He had eight sacks in the final eight games, including the playoffs, and continued to wreak havoc against the run.

"Spencer was playing better than anybody on our defense at the end of last year," inside linebacker Keith Brooking said, quite a statement considering the presence of All-Pros Ware and Jay Ratliff in the Dallas front seven.

The Cowboys hoped Jenkins and Spencer would be good in their first seasons as starters in 2009. They exceeded expectations, making the Cowboys look smart for moving high-paid veterans off the roster to make room in the starting lineup for the recent first-round picks.

Jenkins and Spencer are expected to be elite now. If that happens, one of the league's best defenses will be even better.

Tim MacMahon covers the Cowboys for ESPN Dallas. You can follow him on Twitter or leave a question for his weekly mailbag.