Carson Palmer Arizona Cardinals
Carson Palmer is 14-6 with the Arizona Cardinals. Reuters/Cary Edmondson-USA TODAY Sports

Before the start of the 2014 season, the Dallas Cowboys and Arizona Cardinals weren't expected to finish in the top half of their respective divisions, let alone contend in the NFC. Heading into their Week 9 matchup, the two teams have the best records in the conference.

Arizona might be the biggest surprise of the season. Competing in the NFC West alongside last year's NFC Championship contestants, the Cardinals find themselves in first place with wins in six of their first seven games.

The Cowboys are on pace for 12 wins, making a statement with a victory over the defending champion Seattle Seahawks in Week 6. Even after a loss to the Washington Redskins on Monday night, the Cowboys remain atop the NFC East.

After a hot start, the Cowboys are facing their first significant obstacle of the season. In the team's last loss, quarterback Tony Romo missed a portion of the game with a back injury. The ailment isn't related to the surgery he underwent in December, but it could affect his performance going forward.

Cowboys head coach Jason Garret has described the injury as a bone contusion, saying Romo hasn't been ruled out of Sunday's contest. Romo won't practice this week, but he's stated that he'll be on the field if he can withstand the pain.

Whether Romo or backup Brandon Weeden gets the start, Dallas could have trouble moving the football through the air. Romo did not play well in his return against the Redskins, and Weeden has never been a consistent performer. In 23 games with the Cleveland Browns, he threw 23 touchdowns and 26 interceptions. His career passer rating is 72.5, which would be good for 30th in the league this year.

With so much uncertainty at the quarterback position, Dallas may have to rely even more on DeMarco Murray. The running back has shown the ability to carry the offense, having separated himself as a top MVP candidate. His 1,054 rushing yards are 288 more than the league's No.2 rusher.

If any team has a chance to finally hold Murray under 100 yards rushing, it might be the Cardinals. Arizona ranks second in rushing yards allowed and tied for first in opponents' yards per carry.

No running back has reached the century mark against the Cardinals in seven games, with LeSean McCoy having the best game with 83 yards on the ground. Every other rusher to go up against Arizona's defense has been held under 64 yards.

The Cowboys are favored by four points at several Las Vegas casinos, but even with a healthy Romo, "America's Team" would likely have to look for Murray to have a big game. The Cardinals rank dead last in passing yards allowed, but those numbers don't tell the whole story.

Because Arizona's run defense has been so good, teams are forced to throw more against the Cardinals, resulting in more total yardage. Arizona ranks seventh in passing attempts allowed, even though 18 teams have played one more game than them.

The Cardinals do a terrific job of forcing opposing quarterbacks to make mistakes. They are tied for third with 10 interceptions, and their opponents' 86.2 passer rating is tied for 10th in the league.

Considering Romo's injury and Arizona's fifth-ranked scoring defense, there's a good chance the game will fall below the over/under of 48 total points. The Denver Broncos are the only team to score more than 20 points against the Cardinals, and Dallas scored exactly 17 points in both of their losses.

PREDICTION: Arizona over Dallas, 24-20