IRVING – Stopping the run will be essential to the Cowboys' push in the last two months of the season.

The Cowboys are ranked 17th against the run in the NFL. Over the last three weeks, they have given up 428 yards on 88 carries.

Inside linebacker Zach Thomas didn't have any clear answers as to why the Cowboys run defense has struggled.

"Teams are sticking with their run against us, and it's because we haven't stopped it," Thomas said. "So, we got to stop it and make them throw the ball a little bit more."

One of the more revealing moments for the Cowboys defense came last week, when rookie cornerback Mike Jenkins failed to put a hit on Giants running back Derrick Ward as he ran into the end zone for a fourth-quarter touchdown.

Coach Wade Phillips wouldn't call Jenkins by name but hinted that he had a talk with the rookie. Veteran cornerback Anthony Henry said he also spoke to Jenkins about his lack of effort on the play.

"I'd say go get the tackle," Jenkins said. "That'd be the right answer."

To stop the run, defenders must control their gaps, read the play and use good technique.

In a 3-4 defense, linebackers have to be diligent in attacking ball carriers. Against the Giants, Phillips said players tried to tackle 6-4, 264-pound running back Brandon Jacobs up high. He wanted the Cowboys to hit Jacobs low to take his legs from under him and wrap him up. Jacobs rushed for 117 yards on 17 carries with one touchdown.

During the preseason, defensive coordinator Brian Stewart wanted his players to gang-tackle ball carriers, but it's not happening on a consistent basis.

What's also disturbing about the run defense is the amount of first downs and big plays it has given up.

In the last three weeks, the Cowboys have given up 25 first downs on runs; in the previous six games the team allowed 28.

The Cowboys have given up 11 run plays of 10 or more yards in the last three games and three of those have gone for touchdowns. In the previous six games, the Cowboys had given up only 11 runs of 10 or more yards with no touchdowns.

And next week, the Cowboys face the Redskins and running back Clinton Portis, who leads the NFL with 995 rushing yards.

"The big plays are the ones that hurt you overall," Phillips said. "We played a lot of plays really well. That was probably the big thing. When you have the long run, that makes a difference in your run defense."