The Dallas Cowboys are showing signs that they could have one of the best defenses for the 2012 NFL season.

Through two preseason games, America's team has been dominant, at times, on defense. Dallas shut out Oakland in Week 1 of the preseason. In the team's second exhibition game, they allowed 28 points to the Charges in a loss, but shut down San Diego with the first-string players on the field.

Most of the damage came late in the game against players who are competing to make the Cowboys roster. San Diego didn't score in the first half, and scored one touchdown in the third quarter.

Cornerback Brandon Carr led the Dallas defensive unit, intercepting Philip Rivers twice. Carr signed with Dallas as a free agent, as part of the organization's attempt to improve the team's weak secondary.

Carr left the Chiefs for a reported $50 million contract with the Cowboys. He replaced Terrance Newman, who struggled in his final season with Dallas.

Opposing quarterbacks picked apart the Cowboys secondary at the end of 2011, as Dallas struggled down the stretch and missed the playoffs. Dallas was 23rd in the league last year, allowing 244.1 passing yards per game. In two games this year, they've allowed 194.5 per contest.

The Raiders are not a top offensive unit, but the Chargers have been one of the highest-scoring teams for years. They were fifth in 2011 at 25.4 points per game.

Along with Carr, rookie Morris Claiborne is expected to change things drastically in the Cowboys secondary. The cornerback from LSU made his debut after being selected fifth overall in April's draft. He wasn't tested much, but was satisfied with his performance.

"I was looking for them to come after me every snap," he said. "I just tried to play as honest and as square as I could."

Dallas will have to be ready to stop some of the best quarterbacks in the league. In the NFC East, they'll have to face Eli Manning, Michael Vick and Robert Griffin III six times in all.

It's not just against the pass that the Cowboys have excelled. They have continued to stuff the run. The Raiders and Chargers combined for just 142 rushing yards in the first two preseason games.

If the Cowboys can continue this defensive effort into the regular season, they'll likely be one of the favorites in the NFC. If healthy, they have one of the most explosive offenses in the NFL. Tony Romo, along with a healthy Jason Witten, Miles Austin and Dez Bryant are a difficult tandem to slow down.

Dallas seems to have the pieces to put together a successful season, after missing the playoffs in three of the past four years.