The Cowboys lost Josh Brent for the rest of the year due to the accident that resulted in the death of Jerry Brown. The hole that opened in the defense could have been filled by usual starter Jay Ratliff if he could get healthy enough to return to action. That's not to be, at least for the regular season. Ian Rapoport tweets:

Source: #Cowboys DT Jay Ratliff had surgery this morning for a sports hernia in Philadelphia. 3-6 week recovery. Unclear if he'll head to IR

— Ian Rapoport (@RapSheet) December 13, 2012

This is followed up with more confirmation from the Dallas Morning News. Dallas will have to do battle for the rest of the regular season without its first- and second-string nose tackles. Not exactly an optimistic scenario especially in a 3-4 defense. Sean Lissemore took most of the nose tackle snaps in the Bengals game, and likely will have to continue with some help from recent practice squad call-up Rob Callaway. Dallas also added former Browns player Brian Schaefering earlier this week to help with the defensive line rotation.